639980817 has 24 divisors (see below), whose sum is σ = 1005206400. Its totient is φ = 361067616.

The previous prime is 639980801. The next prime is 639980843. The reversal of 639980817 is 718089936.

It is not a de Polignac number, because 639980817 - 2⁴ = 639980801 is a prime.

It is a super-2 number, since 2×639980817² = 819150892255974978, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 639980817.

It is not an unprimeable number, because it can be changed into a prime (639980017) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15942 + ... + 39167.

It is an arithmetic number, because the mean of its divisors is an integer number (41883600).

Almost surely, 2^639980817 is an apocalyptic number.

It is an amenable number.

639980817 is a deficient number, since it is larger than the sum of its proper divisors (365225583).

639980817 is a wasteful number, since it uses less digits than its factorization.

639980817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55205 (or 55198 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 51.

The square root of 639980817 is about 25297.8421411788. The cubic root of 639980817 is about 861.7652658183.

The spelling of 639980817 in words is "six hundred thirty-nine million, nine hundred eighty thousand, eight hundred seventeen".