64640720 has 40 divisors (see below), whose sum is σ = 150883944. Its totient is φ = 25754112.

The previous prime is 64640713. The next prime is 64640753. The reversal of 64640720 is 2704646.

It can be written as a sum of positive squares in 4 ways, for example, as 15808576 + 48832144 = 3976^2 + 6988^2 .

It is a tau number, because it is divible by the number of its divisors (40).

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, 20702 + ... + 23618.

Almost surely, 2^64640720 is an apocalyptic number.

It is an amenable number.

64640720 is an abundant number, since it is smaller than the sum of its proper divisors (86243224).

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

64640720 is a wasteful number, since it uses less digits than its factorization.

64640720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3207 (or 3201 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 29.

The square root of 64640720 is about 8039.9452734456. The cubic root of 64640720 is about 401.3304034939.

The spelling of 64640720 in words is "sixty-four million, six hundred forty thousand, seven hundred twenty".