Append identifying units to numerals with a non-breaking space. Thus write 1 p.m., 12 mph, 51 kg, and 6 ft. The non-breaking space forces the numeral and identifying unit to appear as a single linguistic entity rather than two distinct pieces of information regardless where in the written line they appear. Type the non-breaking space with option-space on Macs and alt-0160 on Windows.
English habit tends to place whole currency symbols before their numerals and fractional currency symbols after their numerals, both without spaces: $5, $0.50, £40, €3.50, and 50¢.