639442540 has 48 divisors (see below), whose sum is σ = 1479179520. Its totient is φ = 230258880.

The previous prime is 639442537. The next prime is 639442561. The reversal of 639442540 is 45244936.

It is a happy number.

639442540 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 639442540.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8551 + ... + 36769.

It is an arithmetic number, because the mean of its divisors is an integer number (30816240).

Almost surely, 2^639442540 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 639442540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (739589760).

639442540 is an abundant number, since it is smaller than the sum of its proper divisors (839736980).

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

639442540 is a wasteful number, since it uses less digits than its factorization.

639442540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28342 (or 28340 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 37.

The square root of 639442540 is about 25287.2011104432. The cubic root of 639442540 is about 861.5235926717.

The spelling of 639442540 in words is "six hundred thirty-nine million, four hundred forty-two thousand, five hundred forty".