# HP Forums

Full Version: 12c program how many factors does a number have
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Haven't you ever wondered how many factors a certain number has? If you have, would you like a quick way to find out on the HP-12c?

Code:
``` Reg 0 = input # Reg 1 = factor count Reg 2 = square root of input # Reg 3 = trial factor Enter the number you are curious about and press R/S.  On the newer 12c+, it will give you the answer very quickly; on the older ones, a bit longer. The RPN program is only 28 lines long (a perfect number, by the way). 01 STO 0 02 SQRT X 03 STO 2 04 FRAC 05 X=0 06 GOTO 09 07 2 08 GOTO 10 09 1 10 STO 1 11 2 12 STO 3 13 RCL 0 14 X<-->Y 15 / 16 FRAC 17 X=0 18 GOTO 20 19 GOTO 22 20 2 21 STO+1 22 1 23 STO+3 24 RCL 2 25 RCL 3 26 X<=Y 27 GOTO 13 28 RCL 1```

I once learned a quick way to determine the number of factors a number has using pencil and paper. Do the prime factorization of the number. Then, add 1 to the exponent of each prime factor and multiply these numbers together. The answer is the number of factors that the number has.
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