644634531 has 24 divisors (see below), whose sum is σ = 982013760. Its totient is φ = 422462952.

The previous prime is 644634517. The next prime is 644634541. The reversal of 644634531 is 135436446.

644634531 is a `hidden beast` number, since 64 + 4 + 63 + 4 + 531 = 666.

It is not a de Polignac number, because 644634531 - 2⁵ = 644634499 is a prime.

It is a super-2 number, since 2×644634531² = 831107357115179922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644634511) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8145 + ... + 36818.

It is an arithmetic number, because the mean of its divisors is an integer number (40917240).

Almost surely, 2^644634531 is an apocalyptic number.

644634531 is a deficient number, since it is larger than the sum of its proper divisors (337379229).

644634531 is an equidigital number, since it uses as much as digits as its factorization.

644634531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45037 (or 45025 counting only the distinct ones).

The product of its digits is 103680, while the sum is 36.

The square root of 644634531 is about 25389.6540149723. The cubic root of 644634531 is about 863.8490404659.

The spelling of 644634531 in words is "six hundred forty-four million, six hundred thirty-four thousand, five hundred thirty-one".