644775651 has 12 divisors (see below), whose sum is σ = 1002984528. Its totient is φ = 396784944.

The previous prime is 644775631. The next prime is 644775667. The reversal of 644775651 is 156577446.

It is not a de Polignac number, because 644775651 - 2⁹ = 644775139 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644775597 and 644775606.

It is not an unprimeable number, because it can be changed into a prime (644775601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2755335 + ... + 2755568.

It is an arithmetic number, because the mean of its divisors is an integer number (83582044).

Almost surely, 2^644775651 is an apocalyptic number.

644775651 is a deficient number, since it is larger than the sum of its proper divisors (358208877).

644775651 is a wasteful number, since it uses less digits than its factorization.

644775651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5510922 (or 5510919 counting only the distinct ones).

The product of its digits is 705600, while the sum is 45.

The square root of 644775651 is about 25392.4329476323. The cubic root of 644775651 is about 863.9120722956.

The spelling of 644775651 in words is "six hundred forty-four million, seven hundred seventy-five thousand, six hundred fifty-one".