639681507 has 12 divisors (see below), whose sum is σ = 955846320. Its totient is φ = 411748848.

The previous prime is 639681479. The next prime is 639681527. The reversal of 639681507 is 705186936.

It is a happy number.

639681507 is a `hidden beast` number, since 63 + 9 + 6 + 81 + 507 = 666.

It is not a de Polignac number, because 639681507 - 2⁶ = 639681443 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639681527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1225183 + ... + 1225704.

It is an arithmetic number, because the mean of its divisors is an integer number (79653860).

Almost surely, 2^639681507 is an apocalyptic number.

639681507 is a deficient number, since it is larger than the sum of its proper divisors (316164813).

639681507 is a wasteful number, since it uses less digits than its factorization.

639681507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2450922 (or 2450919 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The square root of 639681507 is about 25291.9257273937. The cubic root of 639681507 is about 861.6308997164.

The spelling of 639681507 in words is "six hundred thirty-nine million, six hundred eighty-one thousand, five hundred seven".