639840817 has 16 divisors (see below), whose sum is σ = 816279552. Its totient is φ = 486979920.

The previous prime is 639840787. The next prime is 639840863. The reversal of 639840817 is 718048936.

It is a happy number.

It is not a de Polignac number, because 639840817 - 2¹⁵ = 639808049 is a prime.

It is a super-3 number, since 3×639840817³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (639820817) 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, 93313 + ... + 99934.

It is an arithmetic number, because the mean of its divisors is an integer number (51017472).

Almost surely, 2^639840817 is an apocalyptic number.

It is an amenable number.

639840817 is a deficient number, since it is larger than the sum of its proper divisors (176438735).

639840817 is a wasteful number, since it uses less digits than its factorization.

639840817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193308.

The product of its (nonzero) digits is 290304, while the sum is 46.

The square root of 639840817 is about 25295.0749554138. The cubic root of 639840817 is about 861.7024223014.

The spelling of 639840817 in words is "six hundred thirty-nine million, eight hundred forty thousand, eight hundred seventeen".