639121936 has 40 divisors (see below), whose sum is σ = 1323230040. Its totient is φ = 297990144.

The previous prime is 639121921. The next prime is 639121937.

639121936 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in 4 ways, for example, as 100881936 + 538240000 = 10044^2 + 23200^2 .

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (639121937) 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, 18870 + ... + 40426.

It is an arithmetic number, because the mean of its divisors is an integer number (33080751).

Almost surely, 2^639121936 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639121936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (661615020).

639121936 is an abundant number, since it is smaller than the sum of its proper divisors (684108104).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639121936 is a wasteful number, since it uses less digits than its factorization.

639121936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21691 (or 21685 counting only the distinct ones).

The product of its digits is 52488, while the sum is 40.

The square root of 639121936 is about 25280.8610612851. The cubic root of 639121936 is about 861.3795849007.

The spelling of 639121936 in words is "six hundred thirty-nine million, one hundred twenty-one thousand, nine hundred thirty-six".