644683213 has 4 divisors (see below), whose sum is σ = 652843840. Its totient is φ = 636522588.

The previous prime is 644683189. The next prime is 644683271. The reversal of 644683213 is 312386446.

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.

It is a cyclic number.

It is not a de Polignac number, because 644683213 - 2²⁹ = 107812301 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 (644686213) 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, 4080195 + ... + 4080352.

It is an arithmetic number, because the mean of its divisors is an integer number (163210960).

Almost surely, 2^644683213 is an apocalyptic number.

It is an amenable number.

644683213 is a deficient number, since it is larger than the sum of its proper divisors (8160627).

644683213 is an equidigital number, since it uses as much as digits as its factorization.

644683213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8160626.

The product of its digits is 82944, while the sum is 37.

The square root of 644683213 is about 25390.6126944586. The cubic root of 644683213 is about 863.8707855211.

The spelling of 644683213 in words is "six hundred forty-four million, six hundred eighty-three thousand, two hundred thirteen".