645724431 has 12 divisors (see below), whose sum is σ = 1017505320. Its totient is φ = 391348080.

The previous prime is 645724423. The next prime is 645724487. The reversal of 645724431 is 134427546.

645724431 is a `hidden beast` number, since 645 + 7 + 2 + 4 + 4 + 3 + 1 = 666.

It is not a de Polignac number, because 645724431 - 2³ = 645724423 is a prime.

It is a super-2 number, since 2×645724431² = 833920081580547522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645724031) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3261136 + ... + 3261333.

It is an arithmetic number, because the mean of its divisors is an integer number (84792110).

Almost surely, 2^645724431 is an apocalyptic number.

645724431 is a deficient number, since it is larger than the sum of its proper divisors (371780889).

645724431 is a wasteful number, since it uses less digits than its factorization.

645724431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6522486 (or 6522483 counting only the distinct ones).

The product of its digits is 80640, while the sum is 36.

The square root of 645724431 is about 25411.1084173831. The cubic root of 645724431 is about 864.3356101994.

The spelling of 645724431 in words is "six hundred forty-five million, seven hundred twenty-four thousand, four hundred thirty-one".