639524521 has 4 divisors (see below), whose sum is σ = 641135812. Its totient is φ = 637913232.

The previous prime is 639524489. The next prime is 639524531. The reversal of 639524521 is 125425936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 408484521 + 231040000 = 20211^2 + 15200^2 .

It is a cyclic number.

It is not a de Polignac number, because 639524521 - 2⁵ = 639524489 is a prime.

It is a super-2 number, since 2×639524521² = 817983225920558882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639524531) 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, 805050 + ... + 805843.

It is an arithmetic number, because the mean of its divisors is an integer number (160283953).

Almost surely, 2^639524521 is an apocalyptic number.

It is an amenable number.

639524521 is a deficient number, since it is larger than the sum of its proper divisors (1611291).

639524521 is a wasteful number, since it uses less digits than its factorization.

639524521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1611290.

The product of its digits is 64800, while the sum is 37.

The square root of 639524521 is about 25288.8220563948. The cubic root of 639524521 is about 861.5604088791.

The spelling of 639524521 in words is "six hundred thirty-nine million, five hundred twenty-four thousand, five hundred twenty-one".