644994036 has 48 divisors (see below), whose sum is σ = 1691020800. Its totient is φ = 212579136.

The previous prime is 644994013. The next prime is 644994131. The reversal of 644994036 is 630499446.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 644993982 and 644994000.

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 in 15 ways as a sum of consecutive naturals, for example, 23940 + ... + 43163.

It is an arithmetic number, because the mean of its divisors is an integer number (35229600).

Almost surely, 2^644994036 is an apocalyptic number.

It is an amenable number.

644994036 is an abundant number, since it is smaller than the sum of its proper divisors (1046026764).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644994036 is a wasteful number, since it uses less digits than its factorization.

644994036 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67205 (or 67197 counting only the distinct ones).

The product of its (nonzero) digits is 559872, while the sum is 45.

The square root of 644994036 is about 25396.7327819938. The cubic root of 644994036 is about 864.0095967298.

The spelling of 644994036 in words is "six hundred forty-four million, nine hundred ninety-four thousand, thirty-six".