644638958 has 4 divisors (see below), whose sum is σ = 966958440. Its totient is φ = 322319478.

The previous prime is 644638949. The next prime is 644638979. The reversal of 644638958 is 859836446.

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

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161159738 + ... + 161159741.

It is an arithmetic number, because the mean of its divisors is an integer number (241739610).

Almost surely, 2^644638958 is an apocalyptic number.

644638958 is a deficient number, since it is larger than the sum of its proper divisors (322319482).

644638958 is a wasteful number, since it uses less digits than its factorization.

644638958 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322319481.

The product of its digits is 4976640, while the sum is 53.

The square root of 644638958 is about 25389.7411960028. The cubic root of 644638958 is about 863.8510179435.

The spelling of 644638958 in words is "six hundred forty-four million, six hundred thirty-eight thousand, nine hundred fifty-eight".