639524021 has 16 divisors (see below), whose sum is σ = 698300160. Its totient is φ = 583588800.

The previous prime is 639523999. The next prime is 639524033. The reversal of 639524021 is 120425936.

It is a happy number.

It is not a de Polignac number, because 639524021 - 2¹⁴ = 639507637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639526021) 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, 66500 + ... + 75506.

It is an arithmetic number, because the mean of its divisors is an integer number (43643760).

Almost surely, 2^639524021 is an apocalyptic number.

It is an amenable number.

639524021 is a deficient number, since it is larger than the sum of its proper divisors (58776139).

639524021 is a wasteful number, since it uses less digits than its factorization.

639524021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9164.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 639524021 is about 25288.8121706022. The cubic root of 639524021 is about 861.5601843475.

Adding to 639524021 its reverse (120425936), we get a palindrome (759949957).

The spelling of 639524021 in words is "six hundred thirty-nine million, five hundred twenty-four thousand, twenty-one".