636942816639 has 6 divisors (see below), whose sum is σ = 920028512936. Its totient is φ = 424628544420.

The previous prime is 636942816617. The next prime is 636942816647. The reversal of 636942816639 is 936618249636.

It is a happy number.

636942816639 is a `hidden beast` number, since 63 + 69 + 428 + 1 + 66 + 39 = 666.

It is not a de Polignac number, because 636942816639 - 2⁵ = 636942816607 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (636942816739) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35385712027 + ... + 35385712044.

Almost surely, 2^636942816639 is an apocalyptic number.

636942816639 is a deficient number, since it is larger than the sum of its proper divisors (283085696297).

636942816639 is a wasteful number, since it uses less digits than its factorization.

636942816639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70771424077 (or 70771424074 counting only the distinct ones).

The product of its digits is 60466176, while the sum is 63.

The spelling of 636942816639 in words is "six hundred thirty-six billion, nine hundred forty-two million, eight hundred sixteen thousand, six hundred thirty-nine".