644145656 has 32 divisors (see below), whose sum is σ = 1505796480. Its totient is φ = 250965600.

The previous prime is 644145569. The next prime is 644145673. The reversal of 644145656 is 656541446.

644145656 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 2×644145656² = 829847252287340672, which contains 22 as substring.

It is a Smith number, since the sum of its digits (41) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 522230 + ... + 523461.

It is an arithmetic number, because the mean of its divisors is an integer number (47056140).

Almost surely, 2^644145656 is an apocalyptic number.

It is an amenable number.

644145656 is an abundant number, since it is smaller than the sum of its proper divisors (861650824).

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

644145656 is a wasteful number, since it uses less digits than its factorization.

644145656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1045715 (or 1045711 counting only the distinct ones).

The product of its digits is 345600, while the sum is 41.

The square root of 644145656 is about 25380.0247438808. The cubic root of 644145656 is about 863.6306112724.

The spelling of 644145656 in words is "six hundred forty-four million, one hundred forty-five thousand, six hundred fifty-six".