644706577 has 4 divisors (see below), whose sum is σ = 644961856. Its totient is φ = 644451300.

The previous prime is 644706553. The next prime is 644706593. The reversal of 644706577 is 775607446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 775607446 = 2 ⋅387803723.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644706577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644706277) 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, 123813 + ... + 128914.

It is an arithmetic number, because the mean of its divisors is an integer number (161240464).

Almost surely, 2^644706577 is an apocalyptic number.

It is an amenable number.

644706577 is a deficient number, since it is larger than the sum of its proper divisors (255279).

644706577 is a wasteful number, since it uses less digits than its factorization.

644706577 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255278.

The product of its (nonzero) digits is 987840, while the sum is 46.

The square root of 644706577 is about 25391.0727815900. The cubic root of 644706577 is about 863.8812212580.

The spelling of 644706577 in words is "six hundred forty-four million, seven hundred six thousand, five hundred seventy-seven".