639752721005 has 4 divisors (see below), whose sum is σ = 767703265212. Its totient is φ = 511802176800.

The previous prime is 639752720969. The next prime is 639752721043. The reversal of 639752721005 is 500127257936.

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 287388199396 + 352364521609 = 536086^2 + 593603^2 .

It is not a de Polignac number, because 639752721005 - 2²⁸ = 639484285549 is a prime.

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, 63975272096 + ... + 63975272105.

It is an arithmetic number, because the mean of its divisors is an integer number (191925816303).

Almost surely, 2^639752721005 is an apocalyptic number.

It is an amenable number.

639752721005 is a deficient number, since it is larger than the sum of its proper divisors (127950544207).

639752721005 is a wasteful number, since it uses less digits than its factorization.

639752721005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127950544206.

The product of its (nonzero) digits is 793800, while the sum is 47.

The spelling of 639752721005 in words is "six hundred thirty-nine billion, seven hundred fifty-two million, seven hundred twenty-one thousand, five".