Spy number
A kind of number
About Spy number
A spy number is a positive integer for which the sum of its digits equals the product of its digits (and it has no digit 0, so the product is non-zero). Example: 123 → 1+2+3 = 6 and 1×2×3 = 6.
Key features
- Single-digit numbers 1–9 are trivially spy numbers (sum = product = the digit).
- Sometimes used in puzzles and coding problems.
Examples:
1, 2, 3, 4, 5, 6, 7, 8, 9, 22, 123, 132, 213, 231, 312, 321