644982223 has 4 divisors (see below), whose sum is σ = 648844560. Its totient is φ = 641119888.

The previous prime is 644982211. The next prime is 644982251. The reversal of 644982223 is 322289446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 322289446 = 2 ⋅161144723.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644982223 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644982253) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 1930918 + ... + 1931251.

It is an arithmetic number, because the mean of its divisors is an integer number (162211140).

Almost surely, 2^644982223 is an apocalyptic number.

644982223 is a deficient number, since it is larger than the sum of its proper divisors (3862337).

644982223 is a wasteful number, since it uses less digits than its factorization.

644982223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3862336.

The product of its digits is 165888, while the sum is 40.

The square root of 644982223 is about 25396.5002116433. The cubic root of 644982223 is about 864.0043219484.

The spelling of 644982223 in words is "six hundred forty-four million, nine hundred eighty-two thousand, two hundred twenty-three".