644443 has 2 divisors, whose sum is σ = 644444. Its totient is φ = 644442.

The previous prime is 644431. The next prime is 644447. The reversal of 644443 is 344446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644443 - 2⁵ = 644411 is a prime.

It is a nialpdrome in base 10.

It is not a weakly prime, because it can be changed into another prime (644447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322221 + 322222.

It is an arithmetic number, because the mean of its divisors is an integer number (322222).

2⁶⁴⁴⁴⁴³ is an apocalyptic number.

644443 is a deficient number, since it is larger than the sum of its proper divisors (1).

644443 is an equidigital number, since it uses as much as digits as its factorization.

644443 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 25.

The square root of 644443 is about 802.7720722596. The cubic root of 644443 is about 86.3763477638.

Adding to 644443 its reverse (344446), we get a palindrome (988889).

The spelling of 644443 in words is "six hundred forty-four thousand, four hundred forty-three".