639937505 has 4 divisors (see below), whose sum is σ = 767925012. Its totient is φ = 511950000.

The previous prime is 639937483. The next prime is 639937517. The reversal of 639937505 is 505739936.

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 284124736 + 355812769 = 16856^2 + 18863^2 .

It is not a de Polignac number, because 639937505 - 2¹⁰ = 639936481 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639937505.

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, 63993746 + ... + 63993755.

It is an arithmetic number, because the mean of its divisors is an integer number (191981253).

Almost surely, 2^639937505 is an apocalyptic number.

It is an amenable number.

639937505 is a deficient number, since it is larger than the sum of its proper divisors (127987507).

639937505 is a wasteful number, since it uses less digits than its factorization.

639937505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127987506.

The product of its (nonzero) digits is 765450, while the sum is 47.

The square root of 639937505 is about 25296.9860853027. The cubic root of 639937505 is about 861.7458248089.

The spelling of 639937505 in words is "six hundred thirty-nine million, nine hundred thirty-seven thousand, five hundred five".