639994851 has 10 divisors (see below), whose sum is σ = 956041812. Its totient is φ = 426663180.

The previous prime is 639994829. The next prime is 639994877. The reversal of 639994851 is 158499936.

639994851 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 639994851 - 2⁵ = 639994819 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639994891) 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, 3950505 + ... + 3950666.

Almost surely, 2^639994851 is an apocalyptic number.

639994851 is a deficient number, since it is larger than the sum of its proper divisors (316046961).

639994851 is an equidigital number, since it uses as much as digits as its factorization.

639994851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7901183 (or 7901174 counting only the distinct ones).

The product of its digits is 2099520, while the sum is 54.

The square root of 639994851 is about 25298.1195150944. The cubic root of 639994851 is about 861.7715649265.

The spelling of 639994851 in words is "six hundred thirty-nine million, nine hundred ninety-four thousand, eight hundred fifty-one".