644704066 has 4 divisors (see below), whose sum is σ = 967056102. Its totient is φ = 322352032.

The previous prime is 644704061. The next prime is 644704079. The reversal of 644704066 is 660407446.

644704066 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in only one way, i.e., 593166025 + 51538041 = 24355^2 + 7179^2 .

It is not an unprimeable number, because it can be changed into a prime (644704061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161176015 + ... + 161176018.

Almost surely, 2^644704066 is an apocalyptic number.

644704066 is a deficient number, since it is larger than the sum of its proper divisors (322352036).

644704066 is a wasteful number, since it uses less digits than its factorization.

644704066 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322352035.

The product of its (nonzero) digits is 96768, while the sum is 37.

The square root of 644704066 is about 25391.0233350293. The cubic root of 644704066 is about 863.8800997098.

The spelling of 644704066 in words is "six hundred forty-four million, seven hundred four thousand, sixty-six".