639239881 has 4 divisors (see below), whose sum is σ = 730559872. Its totient is φ = 547919892.

The previous prime is 639239879. The next prime is 639239891. The reversal of 639239881 is 188932936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 639239881 - 2¹ = 639239879 is a prime.

It is a super-2 number, since 2×639239881² = 817255250921788322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (639239891) 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, 45659985 + ... + 45659998.

It is an arithmetic number, because the mean of its divisors is an integer number (182639968).

Almost surely, 2^639239881 is an apocalyptic number.

It is an amenable number.

639239881 is a deficient number, since it is larger than the sum of its proper divisors (91319991).

639239881 is an equidigital number, since it uses as much as digits as its factorization.

639239881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91319990.

The product of its digits is 559872, while the sum is 49.

The square root of 639239881 is about 25283.1936471641. The cubic root of 639239881 is about 861.4325686171.

The spelling of 639239881 in words is "six hundred thirty-nine million, two hundred thirty-nine thousand, eight hundred eighty-one".