666440664 has 64 divisors (see below), whose sum is σ = 1766901600. Its totient is φ = 208748544.

The previous prime is 666440657. The next prime is 666440669. The reversal of 666440664 is 466044666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666440669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 446832 + ... + 448320.

Almost surely, 2^666440664 is an apocalyptic number.

It is an amenable number.

666440664 is an abundant number, since it is smaller than the sum of its proper divisors (1100460936).

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

666440664 is a wasteful number, since it uses less digits than its factorization.

666440664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2612 (or 2608 counting only the distinct ones).

The product of its (nonzero) digits is 497664, while the sum is 42.

The square root of 666440664 is about 25815.5120809176. The cubic root of 666440664 is about 873.4817378219.

It can be divided in two parts, 666 and 440664, that added together give a triangular number (441330 = T₉₃₉).

The spelling of 666440664 in words is "six hundred sixty-six million, four hundred forty thousand, six hundred sixty-four".