639318921 has 8 divisors (see below), whose sum is σ = 879922944. Its totient is φ = 412463760.

The previous prime is 639318853. The next prime is 639318929. The reversal of 639318921 is 129813936.

639318921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 639318921 - 2¹⁷ = 639187849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639318929) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3437106 + ... + 3437291.

It is an arithmetic number, because the mean of its divisors is an integer number (109990368).

Almost surely, 2^639318921 is an apocalyptic number.

It is an amenable number.

639318921 is a deficient number, since it is larger than the sum of its proper divisors (240604023).

639318921 is a wasteful number, since it uses less digits than its factorization.

639318921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6874431.

The product of its digits is 69984, while the sum is 42.

The square root of 639318921 is about 25284.7566925213. The cubic root of 639318921 is about 861.4680716295.

The spelling of 639318921 in words is "six hundred thirty-nine million, three hundred eighteen thousand, nine hundred twenty-one".