639544644 has 36 divisors (see below), whose sum is σ = 1617396144. Its totient is φ = 213080112.

The previous prime is 639544643. The next prime is 639544721. The reversal of 639544644 is 446445936.

639544644 is a `hidden beast` number, since 63 + 9 + 544 + 6 + 44 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a self number, because there is not a number n which added to its sum of digits gives 639544644.

It is not an unprimeable number, because it can be changed into a prime (639544643) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 138379 + ... + 142925.

Almost surely, 2^639544644 is an apocalyptic number.

It is an amenable number.

639544644 is an abundant number, since it is smaller than the sum of its proper divisors (977851500).

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

639544644 is a wasteful number, since it uses less digits than its factorization.

639544644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8464 (or 8459 counting only the distinct ones).

The product of its digits is 1244160, while the sum is 45.

The square root of 639544644 is about 25289.2199167946. The cubic root of 639544644 is about 861.5694452791.

The spelling of 639544644 in words is "six hundred thirty-nine million, five hundred forty-four thousand, six hundred forty-four".