639985015 has 4 divisors (see below), whose sum is σ = 767982024. Its totient is φ = 511988008.

The previous prime is 639985013. The next prime is 639985033. The reversal of 639985015 is 510589936.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 639985015 - 2¹ = 639985013 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 (639985013) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63998497 + ... + 63998506.

It is an arithmetic number, because the mean of its divisors is an integer number (191995506).

Almost surely, 2^639985015 is an apocalyptic number.

639985015 is a deficient number, since it is larger than the sum of its proper divisors (127997009).

639985015 is a wasteful number, since it uses less digits than its factorization.

639985015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127997008.

The product of its (nonzero) digits is 291600, while the sum is 46.

The square root of 639985015 is about 25297.9251125463. The cubic root of 639985015 is about 861.7671500845.

The spelling of 639985015 in words is "six hundred thirty-nine million, nine hundred eighty-five thousand, fifteen".