644220968 has 24 divisors (see below), whose sum is σ = 1215238350. Its totient is φ = 320163072.

The previous prime is 644220959. The next prime is 644220977. The reversal of 644220968 is 869022446.

It is an interprime number because it is at equal distance from previous prime (644220959) and next prime (644220977).

It can be written as a sum of positive squares in 3 ways, for example, as 644042884 + 178084 = 25378^2 + 422^2 .

It is a super-2 number, since 2×644220968² = 830041311221714048, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1086080 + ... + 1086672.

Almost surely, 2^644220968 is an apocalyptic number.

It is an amenable number.

644220968 is a deficient number, since it is larger than the sum of its proper divisors (571017382).

644220968 is an equidigital number, since it uses as much as digits as its factorization.

644220968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1421 (or 824 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 41.

The square root of 644220968 is about 25381.5083870128. The cubic root of 644220968 is about 863.6642678495.

The spelling of 644220968 in words is "six hundred forty-four million, two hundred twenty thousand, nine hundred sixty-eight".