644900660 has 24 divisors (see below), whose sum is σ = 1425570720. Its totient is φ = 244383264.

The previous prime is 644900653. The next prime is 644900681. The reversal of 644900660 is 66009446.

It is a super-2 number, since 2×644900660² = 831793722536871200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 644900660.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 848174 + ... + 848933.

It is an arithmetic number, because the mean of its divisors is an integer number (59398780).

Almost surely, 2^644900660 is an apocalyptic number.

It is an amenable number.

644900660 is an abundant number, since it is smaller than the sum of its proper divisors (780670060).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644900660 is a wasteful number, since it uses less digits than its factorization.

644900660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1697135 (or 1697133 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 35.

The square root of 644900660 is about 25394.8943687506. The cubic root of 644900660 is about 863.9679003992.

The spelling of 644900660 in words is "six hundred forty-four million, nine hundred thousand, six hundred sixty".