644463998 has 4 divisors (see below), whose sum is σ = 966696000. Its totient is φ = 322231998.

The previous prime is 644463977. The next prime is 644464001. The reversal of 644463998 is 899364446.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161115998 + ... + 161116001.

It is an arithmetic number, because the mean of its divisors is an integer number (241674000).

Almost surely, 2^644463998 is an apocalyptic number.

644463998 is a deficient number, since it is larger than the sum of its proper divisors (322232002).

644463998 is a wasteful number, since it uses less digits than its factorization.

644463998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322232001.

The product of its digits is 4478976, while the sum is 53.

The square root of 644463998 is about 25386.2954761028. The cubic root of 644463998 is about 863.7728589224.

The spelling of 644463998 in words is "six hundred forty-four million, four hundred sixty-three thousand, nine hundred ninety-eight".