639521 has 8 divisors (see below), whose sum is σ = 682080. Its totient is φ = 597888.

The previous prime is 639517. The next prime is 639533. The reversal of 639521 is 125936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 639521 - 2² = 639517 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (639511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1670 + ... + 2016.

It is an arithmetic number, because the mean of its divisors is an integer number (85260).

2⁶³⁹⁵²¹ is an apocalyptic number.

It is an amenable number.

639521 is a deficient number, since it is larger than the sum of its proper divisors (42559).

639521 is a wasteful number, since it uses less digits than its factorization.

639521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 463.

The product of its digits is 1620, while the sum is 26.

The square root of 639521 is about 799.7005689632. The cubic root of 639521 is about 86.1558827725.

The spelling of 639521 in words is "six hundred thirty-nine thousand, five hundred twenty-one".