639681385 has 16 divisors (see below), whose sum is σ = 898676352. Its totient is φ = 427939200.

The previous prime is 639681377. The next prime is 639681431. The reversal of 639681385 is 583186936.

It is not a de Polignac number, because 639681385 - 2³ = 639681377 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 221451 + ... + 224320.

It is an arithmetic number, because the mean of its divisors is an integer number (56167272).

Almost surely, 2^639681385 is an apocalyptic number.

It is an amenable number.

639681385 is a deficient number, since it is larger than the sum of its proper divisors (258994967).

639681385 is a wasteful number, since it uses less digits than its factorization.

639681385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 445824.

The product of its digits is 933120, while the sum is 49.

The square root of 639681385 is about 25291.9233155567. The cubic root of 639681385 is about 861.6308449396.

The spelling of 639681385 in words is "six hundred thirty-nine million, six hundred eighty-one thousand, three hundred eighty-five".