# 645

From Number

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## Summary

### Factorization

The number 645 is a square-free number with prime factors 3, 5, and 43:

### Properties and families

Property or family | Parameter values | First few numbers satisfying the property | Proof of satisfaction/containment/membership |
---|---|---|---|

Poulet number (also called Sarrus number) (Fermat pseudoprime to base 2) | third Poulet number | 341, 561, 645, 1105, 1387, 1729, 1905, 2047, [SHOW MORE] View list on OEIS |
, and 28 divides 644, so . |