644455978 has 8 divisors (see below), whose sum is σ = 969377760. Its totient is φ = 321330060.

The previous prime is 644455957. The next prime is 644455979. The reversal of 644455978 is 879554446.

644455978 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (644455979) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 448068 + ... + 449503.

It is an arithmetic number, because the mean of its divisors is an integer number (121172220).

Almost surely, 2^644455978 is an apocalyptic number.

644455978 is a deficient number, since it is larger than the sum of its proper divisors (324921782).

644455978 is a wasteful number, since it uses less digits than its factorization.

644455978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 897932.

The product of its digits is 4838400, while the sum is 52.

The square root of 644455978 is about 25386.1375163690. The cubic root of 644455978 is about 863.7692758482.

The spelling of 644455978 in words is "six hundred forty-four million, four hundred fifty-five thousand, nine hundred seventy-eight".