644704166 has 4 divisors (see below), whose sum is σ = 967056252. Its totient is φ = 322352082.

The previous prime is 644704157. The next prime is 644704171. The reversal of 644704166 is 661407446.

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 (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161176040 + ... + 161176043.

It is an arithmetic number, because the mean of its divisors is an integer number (241764063).

Almost surely, 2^644704166 is an apocalyptic number.

644704166 is a deficient number, since it is larger than the sum of its proper divisors (322352086).

644704166 is a wasteful number, since it uses less digits than its factorization.

644704166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322352085.

The product of its (nonzero) digits is 96768, while the sum is 38.

The square root of 644704166 is about 25391.0253042291. The cubic root of 644704166 is about 863.8801443753.

The spelling of 644704166 in words is "six hundred forty-four million, seven hundred four thousand, one hundred sixty-six".