639856921773 has 32 divisors (see below), whose sum is σ = 884265338880. Its totient is φ = 411326023680.

The previous prime is 639856921757. The next prime is 639856921811. The reversal of 639856921773 is 377129658936.

It is not a de Polignac number, because 639856921773 - 2⁴ = 639856921757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639856921723) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2442861 + ... + 2692077.

It is an arithmetic number, because the mean of its divisors is an integer number (27633291840).

Almost surely, 2^639856921773 is an apocalyptic number.

It is an amenable number.

639856921773 is a deficient number, since it is larger than the sum of its proper divisors (244408417107).

639856921773 is a wasteful number, since it uses less digits than its factorization.

639856921773 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249537.

The product of its digits is 102876480, while the sum is 66.

The spelling of 639856921773 in words is "six hundred thirty-nine billion, eight hundred fifty-six million, nine hundred twenty-one thousand, seven hundred seventy-three".