644818636036 has 27 divisors (see below), whose sum is σ = 1132785945333. Its totient is φ = 321170279760.

The previous prime is 644818635997. The next prime is 644818636057. The reversal of 644818636036 is 630636818446.

The square root of 644818636036 is 803006.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 26305596100 + 618513039936 = 162190^2 + 786456^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 531589366 + ... + 531590578.

Almost surely, 2^644818636036 is an apocalyptic number.

644818636036 is the 803006-th square number.

It is an amenable number.

644818636036 is a deficient number, since it is larger than the sum of its proper divisors (487967309297).

644818636036 is an frugal number, since it uses more digits than its factorization.

644818636036 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3092 (or 1546 counting only the distinct ones).

The product of its (nonzero) digits is 11943936, while the sum is 55.

The spelling of 644818636036 in words is "six hundred forty-four billion, eight hundred eighteen million, six hundred thirty-six thousand, thirty-six".