639381621 has 8 divisors (see below), whose sum is σ = 854140960. Its totient is φ = 425438352.

The previous prime is 639381583. The next prime is 639381653. The reversal of 639381621 is 126183936.

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

It is not a de Polignac number, because 639381621 - 2⁶ = 639381557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 639381621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639381671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 202186 + ... + 205323.

It is an arithmetic number, because the mean of its divisors is an integer number (106767620).

Almost surely, 2^639381621 is an apocalyptic number.

It is an amenable number.

639381621 is a deficient number, since it is larger than the sum of its proper divisors (214759339).

639381621 is a wasteful number, since it uses less digits than its factorization.

639381621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 408035.

The product of its digits is 46656, while the sum is 39.

The square root of 639381621 is about 25285.9965395869. The cubic root of 639381621 is about 861.4962329955.

The spelling of 639381621 in words is "six hundred thirty-nine million, three hundred eighty-one thousand, six hundred twenty-one".