666865720 has 16 divisors (see below), whose sum is σ = 1500447960. Its totient is φ = 266746272.

The previous prime is 666865709. The next prime is 666865729. The reversal of 666865720 is 27568666.

It is a super-2 number, since 2×666865720² = 889419777022236800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666865729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8335782 + ... + 8335861.

Almost surely, 2^666865720 is an apocalyptic number.

It is an amenable number.

666865720 is an abundant number, since it is smaller than the sum of its proper divisors (833582240).

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

666865720 is a wasteful number, since it uses less digits than its factorization.

666865720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16671654 (or 16671650 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 46.

The square root of 666865720 is about 25823.7433382537. The cubic root of 666865720 is about 873.6674006362.

The spelling of 666865720 in words is "six hundred sixty-six million, eight hundred sixty-five thousand, seven hundred twenty".