644725646 has 16 divisors (see below), whose sum is σ = 1031350320. Its totient is φ = 301215360.

The previous prime is 644725639. The next prime is 644725687. The reversal of 644725646 is 646527446.

It is a super-2 number, since 2×644725646² = 831342317220234632, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644725597 and 644725606.

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, 63485 + ... + 72936.

It is an arithmetic number, because the mean of its divisors is an integer number (64459395).

Almost surely, 2^644725646 is an apocalyptic number.

644725646 is a deficient number, since it is larger than the sum of its proper divisors (386624674).

644725646 is a wasteful number, since it uses less digits than its factorization.

644725646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136579.

The product of its digits is 967680, while the sum is 44.

The square root of 644725646 is about 25391.4482848064. The cubic root of 644725646 is about 863.8897384084.

The spelling of 644725646 in words is "six hundred forty-four million, seven hundred twenty-five thousand, six hundred forty-six".