645902251 has 2 divisors, whose sum is σ = 645902252. Its totient is φ = 645902250.

The previous prime is 645902141. The next prime is 645902263. The reversal of 645902251 is 152209546.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645902251 is a prime.

It is a super-3 number, since 3×645902251³ (a number of 27 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (645902051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322951125 + 322951126.

It is an arithmetic number, because the mean of its divisors is an integer number (322951126).

Almost surely, 2^645902251 is an apocalyptic number.

645902251 is a deficient number, since it is larger than the sum of its proper divisors (1).

645902251 is an equidigital number, since it uses as much as digits as its factorization.

645902251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 645902251 is about 25414.6070400469. The cubic root of 645902251 is about 864.4149433456.

The spelling of 645902251 in words is "six hundred forty-five million, nine hundred two thousand, two hundred fifty-one".