644243443 has 4 divisors (see below), whose sum is σ = 644910640. Its totient is φ = 643576248.

The previous prime is 644243423. The next prime is 644243447. The reversal of 644243443 is 344342446.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644243443 is a prime.

It is a super-2 number, since 2×644243443² = 830099227696988498, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644243399 and 644243408.

It is not an unprimeable number, because it can be changed into a prime (644243447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 332148 + ... + 334081.

It is an arithmetic number, because the mean of its divisors is an integer number (161227660).

Almost surely, 2^644243443 is an apocalyptic number.

644243443 is a deficient number, since it is larger than the sum of its proper divisors (667197).

644243443 is an equidigital number, since it uses as much as digits as its factorization.

644243443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 667196.

The product of its digits is 110592, while the sum is 34.

The square root of 644243443 is about 25381.9511267357. The cubic root of 644243443 is about 863.6743113127.

Adding to 644243443 its reverse (344342446), we get a palindrome (988585889).

The spelling of 644243443 in words is "six hundred forty-four million, two hundred forty-three thousand, four hundred forty-three".