644817844 has 24 divisors (see below), whose sum is σ = 1251885600. Its totient is φ = 288130080.

The previous prime is 644817827. The next prime is 644817847. The reversal of 644817844 is 448718446.

It is a junction number, because it is equal to n+sod(n) for n = 644817794 and 644817803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644817847) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121599 + ... + 126790.

It is an arithmetic number, because the mean of its divisors is an integer number (52161900).

Almost surely, 2^644817844 is an apocalyptic number.

It is an amenable number.

644817844 is a deficient number, since it is larger than the sum of its proper divisors (607067756).

644817844 is a wasteful number, since it uses less digits than its factorization.

644817844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 248463 (or 248461 counting only the distinct ones).

The product of its digits is 688128, while the sum is 46.

The square root of 644817844 is about 25393.2637524206. The cubic root of 644817844 is about 863.9309161870.

The spelling of 644817844 in words is "six hundred forty-four million, eight hundred seventeen thousand, eight hundred forty-four".