644747444 has 36 divisors (see below), whose sum is σ = 1299106368. Its totient is φ = 277635600.

The previous prime is 644747443. The next prime is 644747471. The reversal of 644747444 is 444747446.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a junction number, because it is equal to n+sod(n) for n = 644747395 and 644747404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644747443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4412 + ... + 36179.

It is an arithmetic number, because the mean of its divisors is an integer number (36086288).

Almost surely, 2^644747444 is an apocalyptic number.

It is an amenable number.

644747444 is an abundant number, since it is smaller than the sum of its proper divisors (654358924).

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

644747444 is a wasteful number, since it uses less digits than its factorization.

644747444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40644 (or 40623 counting only the distinct ones).

The product of its digits is 1204224, while the sum is 44.

The square root of 644747444 is about 25391.8775201835. The cubic root of 644747444 is about 863.8994742583.

The spelling of 644747444 in words is "six hundred forty-four million, seven hundred forty-seven thousand, four hundred forty-four".