644355136 has 28 divisors (see below), whose sum is σ = 1279451340. Its totient is φ = 321973760.

The previous prime is 644355133. The next prime is 644355149. The reversal of 644355136 is 631553446.

It can be written as a sum of positive squares in 2 ways, for example, as 350438400 + 293916736 = 18720^2 + 17144^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644355095 and 644355104.

It is not an unprimeable number, because it can be changed into a prime (644355133) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 184446 + ... + 187906.

Almost surely, 2^644355136 is an apocalyptic number.

It is an amenable number.

644355136 is a deficient number, since it is larger than the sum of its proper divisors (635096204).

644355136 is a wasteful number, since it uses less digits than its factorization.

644355136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6382 (or 6372 counting only the distinct ones).

The product of its digits is 129600, while the sum is 37.

The square root of 644355136 is about 25384.1512759438. The cubic root of 644355136 is about 863.7242203968.

The spelling of 644355136 in words is "six hundred forty-four million, three hundred fifty-five thousand, one hundred thirty-six".