644810940 has 72 divisors (see below), whose sum is σ = 2023388640. Its totient is φ = 166018944.

The previous prime is 644810939. The next prime is 644810983. The reversal of 644810940 is 49018446.

It is a happy number.

644810940 is a `hidden beast` number, since 644 + 8 + 1 + 0 + 9 + 4 + 0 = 666.

644810940 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×644810940² = 831562296687367200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 644810895 and 644810904.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 56544 + ... + 66983.

It is an arithmetic number, because the mean of its divisors is an integer number (28102620).

Almost surely, 2^644810940 is an apocalyptic number.

644810940 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644810940 is an abundant number, since it is smaller than the sum of its proper divisors (1378577700).

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

644810940 is a wasteful number, since it uses less digits than its factorization.

644810940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123571 (or 123566 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The square root of 644810940 is about 25393.1278104923. The cubic root of 644810940 is about 863.9278328354.

The spelling of 644810940 in words is "six hundred forty-four million, eight hundred ten thousand, nine hundred forty".