diff --git a/src/read_data.cpp b/src/read_data.cpp
index a46602d84a..9ec63bddf9 100644
--- a/src/read_data.cpp
+++ b/src/read_data.cpp
@@ -1013,114 +1013,80 @@ void ReadData::header(int firstpass)
 
     // search line for header keyword and set corresponding variable
     // customize for new header lines
-    // check for triangles before angles so "triangles" not matched as "angles"
+
     int extra_flag_value = 0;
-    int rv;
+    auto words = utils::split_words(line);
 
     if (utils::strmatch(line,"^\\s*\\d+\\s+atoms\\s")) {
-      rv = sscanf(line,BIGINT_FORMAT,&natoms);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'atoms' line in data file header");
+      natoms = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->natoms = natoms;
       else if (firstpass) atom->natoms += natoms;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+ellipsoids\\s")) {
-      if (!avec_ellipsoid)
-        error->all(FLERR,"No ellipsoids allowed with this atom style");
-      rv = sscanf(line,BIGINT_FORMAT,&nellipsoids);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'ellipsoids' line in data file header");
+      if (!avec_ellipsoid) error->all(FLERR,"No ellipsoids allowed with this atom style");
+      nellipsoids = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nellipsoids = nellipsoids;
       else if (firstpass) atom->nellipsoids += nellipsoids;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+lines\\s")) {
-      if (!avec_line)
-        error->all(FLERR,"No lines allowed with this atom style");
-      rv =  sscanf(line,BIGINT_FORMAT,&nlines);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'lines' line in data file header");
+      if (!avec_line) error->all(FLERR,"No lines allowed with this atom style");
+      nlines = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nlines = nlines;
       else if (firstpass) atom->nlines += nlines;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+triangles\\s")) {
-      if (!avec_tri)
-        error->all(FLERR,"No triangles allowed with this atom style");
-      rv = sscanf(line,BIGINT_FORMAT,&ntris);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'triangles' line in data file header");
+      if (!avec_tri) error->all(FLERR,"No triangles allowed with this atom style");
+      ntris = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->ntris = ntris;
       else if (firstpass) atom->ntris += ntris;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+bodies\\s")) {
-      if (!avec_body)
-        error->all(FLERR,"No bodies allowed with this atom style");
-      rv = sscanf(line,BIGINT_FORMAT,&nbodies);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'bodies' line in data file header");
+      if (!avec_body) error->all(FLERR,"No bodies allowed with this atom style");
+      nbodies = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nbodies = nbodies;
       else if (firstpass) atom->nbodies += nbodies;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+bonds\\s")) {
-      rv = sscanf(line,BIGINT_FORMAT,&nbonds);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'bonds' line in data file header");
+      nbonds = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nbonds = nbonds;
       else if (firstpass) atom->nbonds += nbonds;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+angles\\s")) {
-      rv = sscanf(line,BIGINT_FORMAT,&nangles);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'angles' line in data file header");
+      nangles = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nangles = nangles;
       else if (firstpass) atom->nangles += nangles;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+dihedrals\\s")) {
-      rv = sscanf(line,BIGINT_FORMAT,&ndihedrals);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'dihedrals' line in data file header");
+      ndihedrals = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->ndihedrals = ndihedrals;
       else if (firstpass) atom->ndihedrals += ndihedrals;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+impropers\\s")) {
-      rv = sscanf(line,BIGINT_FORMAT,&nimpropers);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'impropers' line in data file header");
+      nimpropers = utils::bnumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nimpropers = nimpropers;
       else if (firstpass) atom->nimpropers += nimpropers;
 
     // Atom class type settings are only set by first data file
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+atom\\s+types\\s")) {
-      rv = sscanf(line,"%d",&ntypes);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'atom types' line in data file header");
+      ntypes = utils::inumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->ntypes = ntypes + extra_atom_types;
 
     } else if (utils::strmatch(line,"\\s*\\d+\\s+bond\\s+types\\s")) {
-      rv = sscanf(line,"%d",&nbondtypes);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'bond types' line in data file header");
+      nbondtypes = utils::inumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nbondtypes = nbondtypes + extra_bond_types;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+angle\\s+types\\s")) {
-      rv = sscanf(line,"%d",&nangletypes);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'angle types' line in data file header");
+      nangletypes = utils::inumeric(FLERR, words[0], false, lmp);
       if (addflag == NONE) atom->nangletypes = nangletypes + extra_angle_types;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+dihedral\\s+types\\s")) {
-      rv = sscanf(line,"%d",&ndihedraltypes);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'dihedral types' line in data file header");
-      if (addflag == NONE)
-        atom->ndihedraltypes = ndihedraltypes + extra_dihedral_types;
+      ndihedraltypes = utils::inumeric(FLERR, words[0], false, lmp);
+      if (addflag == NONE) atom->ndihedraltypes = ndihedraltypes + extra_dihedral_types;
 
     } else if (utils::strmatch(line,"^\\s*\\d+\\s+improper\\s+types\\s")) {
-      rv = sscanf(line,"%d",&nimpropertypes);
-      if (rv != 1)
-        error->all(FLERR,"Could not parse 'improper types' line in data file header");
-      if (addflag == NONE)
-        atom->nimpropertypes = nimpropertypes + extra_improper_types;
+      nimpropertypes = utils::inumeric(FLERR, words[0], false, lmp);
+      if (addflag == NONE) atom->nimpropertypes = nimpropertypes + extra_improper_types;
 
     // these settings only used by first data file
     // also, these are obsolescent. we parse them to maintain backward
@@ -1129,45 +1095,41 @@ void ReadData::header(int firstpass)
     // the input and the data file, we use the larger of the two.
 
     } else if (strstr(line,"extra bond per atom")) {
-      if (addflag == NONE) sscanf(line,"%d",&extra_flag_value);
+      if (addflag == NONE) extra_flag_value = utils::inumeric(FLERR, words[0], false, lmp);
       atom->extra_bond_per_atom = MAX(atom->extra_bond_per_atom,extra_flag_value);
     } else if (strstr(line,"extra angle per atom")) {
-      if (addflag == NONE) sscanf(line,"%d",&extra_flag_value);
+      if (addflag == NONE) extra_flag_value = utils::inumeric(FLERR, words[0], false, lmp);
       atom->extra_angle_per_atom = MAX(atom->extra_angle_per_atom,extra_flag_value);
     } else if (strstr(line,"extra dihedral per atom")) {
-      if (addflag == NONE) sscanf(line,"%d",&extra_flag_value);
+      if (addflag == NONE) extra_flag_value = utils::inumeric(FLERR, words[0], false, lmp);
       atom->extra_dihedral_per_atom = MAX(atom->extra_dihedral_per_atom,extra_flag_value);
     } else if (strstr(line,"extra improper per atom")) {
-      if (addflag == NONE) sscanf(line,"%d",&extra_flag_value);
+      if (addflag == NONE) extra_flag_value = utils::inumeric(FLERR, words[0], false, lmp);
       atom->extra_improper_per_atom = MAX(atom->extra_improper_per_atom,extra_flag_value);
     } else if (strstr(line,"extra special per atom")) {
-      if (addflag == NONE) sscanf(line,"%d",&extra_flag_value);
+      if (addflag == NONE) extra_flag_value = utils::inumeric(FLERR, words[0], false, lmp);
       force->special_extra = MAX(force->special_extra,extra_flag_value);
 
     // local copy of box info
     // so can treat differently for first vs subsequent data files
 
     } else if (utils::strmatch(line,"^\\s*\\f+\\s+\\f+\\s+xlo\\s+xhi\\s")) {
-      rv = sscanf(line,"%lg %lg",&boxlo[0],&boxhi[0]);
-      if (rv != 2)
-        error->all(FLERR,"Could not parse 'xlo xhi' line in data file header");
+      boxlo[0] = utils::numeric(FLERR, words[0], false, lmp);
+      boxhi[0] = utils::numeric(FLERR, words[1], false, lmp);
 
     } else if (utils::strmatch(line,"^\\s*\\f+\\s+\\f+\\s+ylo\\s+yhi\\s")) {
-      rv = sscanf(line,"%lg %lg",&boxlo[1],&boxhi[1]);
-      if (rv != 2)
-        error->all(FLERR,"Could not parse 'ylo yhi' line in data file header");
+      boxlo[1] = utils::numeric(FLERR, words[0], false, lmp);
+      boxhi[1] = utils::numeric(FLERR, words[1], false, lmp);
 
     } else if (utils::strmatch(line,"^\\s*\\f+\\s+\\f+\\s+zlo\\s+zhi\\s")) {
-      rv = sscanf(line,"%lg %lg",&boxlo[2],&boxhi[2]);
-      if (rv != 2)
-        error->all(FLERR,"Could not parse 'zlo zhi' line in data file header");
+      boxlo[2] = utils::numeric(FLERR, words[0], false, lmp);
+      boxhi[2] = utils::numeric(FLERR, words[1], false, lmp);
 
-    } else if (utils::strmatch(line,"^\\s*\\f+\\s+\\f+\\s+\\f+"
-                               "\\s+xy\\s+xz\\s+yz\\s")) {
+    } else if (utils::strmatch(line,"^\\s*\\f+\\s+\\f+\\s+\\f+\\s+xy\\s+xz\\s+yz\\s")) {
       triclinic = 1;
-      rv = sscanf(line,"%lg %lg %lg",&xy,&xz,&yz);
-      if (rv != 3)
-        error->all(FLERR,"Could not parse 'xy xz yz' line in data file header");
+      xy = utils::numeric(FLERR, words[0], false, lmp);
+      xz = utils::numeric(FLERR, words[0], false, lmp);
+      yz = utils::numeric(FLERR, words[0], false, lmp);
 
     } else break;
   }
diff --git a/src/reader_native.cpp b/src/reader_native.cpp
index 32b2279a60..efa9709942 100644
--- a/src/reader_native.cpp
+++ b/src/reader_native.cpp
@@ -101,9 +101,7 @@ int ReaderNative::read_time(bigint &ntimestep)
       error->one(FLERR,"Dump file is incorrectly formatted");
 
     read_lines(1);
-    int rv = sscanf(line,BIGINT_FORMAT,&ntimestep);
-    if (rv != 1)
-      error->one(FLERR,"Dump file is incorrectly formatted");
+    ntimestep = utils::bnumeric(FLERR, utils::trim(line), true, lmp);
   }
   return 0;
 }
@@ -140,10 +138,8 @@ void ReaderNative::skip()
 
   } else {
     read_lines(2);
-    bigint natoms;
-    int rv = sscanf(line,BIGINT_FORMAT,&natoms);
-    if (rv != 1) error->one(FLERR,"Dump file is incorrectly formatted");
-
+    // parse natoms value so we error out on incorrectly formatted dumps
+    utils::bnumeric(FLERR, utils::trim(line), true, lmp);
     read_lines(5);
 
     // invoke read_lines() in chunks no larger than MAXSMALLINT