644690443 has 4 divisors (see below), whose sum is σ = 659683288. Its totient is φ = 629697600.

The previous prime is 644690441. The next prime is 644690471. The reversal of 644690443 is 344096446.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 644690443 - 2¹ = 644690441 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644690396 and 644690405.

It is not an unprimeable number, because it can be changed into a prime (644690441) 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, 7496358 + ... + 7496443.

It is an arithmetic number, because the mean of its divisors is an integer number (164920822).

Almost surely, 2^644690443 is an apocalyptic number.

644690443 is a deficient number, since it is larger than the sum of its proper divisors (14992845).

644690443 is a wasteful number, since it uses less digits than its factorization.

644690443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14992844.

The product of its (nonzero) digits is 248832, while the sum is 40.

The square root of 644690443 is about 25390.7550695130. The cubic root of 644690443 is about 863.8740148914.

The spelling of 644690443 in words is "six hundred forty-four million, six hundred ninety thousand, four hundred forty-three".