645265491 has 32 divisors (see below), whose sum is σ = 952304640. Its totient is φ = 388451232.

The previous prime is 645265487. The next prime is 645265493. The reversal of 645265491 is 194562546.

645265491 = 416² + 417² + ... + 1261².

It is not a de Polignac number, because 645265491 - 2² = 645265487 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645265493) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 308736 + ... + 310818.

It is an arithmetic number, because the mean of its divisors is an integer number (29759520).

Almost surely, 2^645265491 is an apocalyptic number.

645265491 is a deficient number, since it is larger than the sum of its proper divisors (307039149).

645265491 is a wasteful number, since it uses less digits than its factorization.

645265491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2172 (or 2146 counting only the distinct ones).

The product of its digits is 259200, while the sum is 42.

The square root of 645265491 is about 25402.0765096084. The cubic root of 645265491 is about 864.1307900105.

The spelling of 645265491 in words is "six hundred forty-five million, two hundred sixty-five thousand, four hundred ninety-one".