644362368 has 128 divisors (see below), whose sum is σ = 1907236800. Its totient is φ = 191385600.

The previous prime is 644362357. The next prime is 644362379. The reversal of 644362368 is 863263446.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (644362357) and next prime (644362379).

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×644362368² = 830405722589134848, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 142543 + ... + 146993.

Almost surely, 2^644362368 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644362368, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (953618400).

644362368 is an abundant number, since it is smaller than the sum of its proper divisors (1262874432).

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

644362368 is a wasteful number, since it uses less digits than its factorization.

644362368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4510 (or 4498 counting only the distinct ones).

The product of its digits is 497664, while the sum is 42.

The square root of 644362368 is about 25384.2937266334. The cubic root of 644362368 is about 863.7274517568.

The spelling of 644362368 in words is "six hundred forty-four million, three hundred sixty-two thousand, three hundred sixty-eight".