66405664 has 24 divisors (see below), whose sum is σ = 140793660. Its totient is φ = 30648576.

The previous prime is 66405641. The next prime is 66405671. The reversal of 66405664 is 46650466.

It can be written as a sum of positive squares in 2 ways, for example, as 65610000 + 795664 = 8100^2 + 892^2 .

It is a super-2 number, since 2×66405664² = 8819424422561792, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 79399 + ... + 80230.

Almost surely, 2^66405664 is an apocalyptic number.

It is an amenable number.

66405664 is an abundant number, since it is smaller than the sum of its proper divisors (74387996).

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

66405664 is a wasteful number, since it uses less digits than its factorization.

66405664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159652 (or 159644 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 37.

The square root of 66405664 is about 8148.9670511053. The cubic root of 66405664 is about 404.9502839954.

The spelling of 66405664 in words is "sixty-six million, four hundred five thousand, six hundred sixty-four".