636942816638 has 4 divisors (see below), whose sum is σ = 955414224960. Its totient is φ = 318471408318.

The previous prime is 636942816617. The next prime is 636942816647. The reversal of 636942816638 is 836618249636.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159235704158 + ... + 159235704161.

It is an arithmetic number, because the mean of its divisors is an integer number (238853556240).

Almost surely, 2^636942816638 is an apocalyptic number.

636942816638 is a deficient number, since it is larger than the sum of its proper divisors (318471408322).

636942816638 is a wasteful number, since it uses less digits than its factorization.

636942816638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 318471408321.

The product of its digits is 53747712, while the sum is 62.

The spelling of 636942816638 in words is "six hundred thirty-six billion, nine hundred forty-two million, eight hundred sixteen thousand, six hundred thirty-eight".