639909477 has 10 divisors (see below), whose sum is σ = 955914278. Its totient is φ = 426606264.

The previous prime is 639909467. The next prime is 639909481. The reversal of 639909477 is 774909936.

It can be written as a sum of positive squares in only one way, i.e., 536663556 + 103245921 = 23166^2 + 10161^2 .

It is a de Polignac number, because none of the positive numbers 2^k-639909477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639909467) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 3949978 + ... + 3950139.

Almost surely, 2^639909477 is an apocalyptic number.

It is an amenable number.

639909477 is a deficient number, since it is larger than the sum of its proper divisors (316004801).

639909477 is an equidigital number, since it uses as much as digits as its factorization.

639909477 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7900129 (or 7900120 counting only the distinct ones).

The product of its (nonzero) digits is 2571912, while the sum is 54.

The square root of 639909477 is about 25296.4321001994. The cubic root of 639909477 is about 861.7332437029.

It can be divided in two parts, 639 and 909477, that added together give a square (910116 = 954²).

The spelling of 639909477 in words is "six hundred thirty-nine million, nine hundred nine thousand, four hundred seventy-seven".