639279381 has 16 divisors (see below), whose sum is σ = 922610304. Its totient is φ = 391401024.

The previous prime is 639279371. The next prime is 639279397. The reversal of 639279381 is 183972936.

It is not a de Polignac number, because 639279381 - 2¹⁰ = 639278357 is a prime.

It is a super-2 number, since 2×639279381² = 817356253943486322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 639279381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639279371) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33921 + ... + 49286.

It is an arithmetic number, because the mean of its divisors is an integer number (57663144).

Almost surely, 2^639279381 is an apocalyptic number.

It is an amenable number.

639279381 is a deficient number, since it is larger than the sum of its proper divisors (283330923).

639279381 is a wasteful number, since it uses less digits than its factorization.

639279381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83420.

The product of its digits is 489888, while the sum is 48.

The square root of 639279381 is about 25283.9747864136. The cubic root of 639279381 is about 861.4503115055.

The spelling of 639279381 in words is "six hundred thirty-nine million, two hundred seventy-nine thousand, three hundred eighty-one".