639565216405 has 4 divisors (see below), whose sum is σ = 767478259692. Its totient is φ = 511652173120.

The previous prime is 639565216327. The next prime is 639565216453. The reversal of 639565216405 is 504612565936.

639565216405 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 144319451236 + 495245765169 = 379894^2 + 703737^2 .

It is not a de Polignac number, because 639565216405 - 2²⁵ = 639531661973 is a prime.

It is a super-2 number, since 2×639565216405² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63956521636 + ... + 63956521645.

It is an arithmetic number, because the mean of its divisors is an integer number (191869564923).

Almost surely, 2^639565216405 is an apocalyptic number.

It is an amenable number.

639565216405 is a deficient number, since it is larger than the sum of its proper divisors (127913043287).

639565216405 is a wasteful number, since it uses less digits than its factorization.

639565216405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127913043286.

The product of its (nonzero) digits is 5832000, while the sum is 52.

The spelling of 639565216405 in words is "six hundred thirty-nine billion, five hundred sixty-five million, two hundred sixteen thousand, four hundred five".