644843 has 2 divisors, whose sum is σ = 644844. Its totient is φ = 644842.

The previous prime is 644837. The next prime is 644857. The reversal of 644843 is 348446.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644843 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322421 + 322422.

It is an arithmetic number, because the mean of its divisors is an integer number (322422).

2⁶⁴⁴⁸⁴³ is an apocalyptic number.

644843 is a deficient number, since it is larger than the sum of its proper divisors (1).

644843 is an equidigital number, since it uses as much as digits as its factorization.

644843 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 29.

The square root of 644843 is about 803.0211703311. The cubic root of 644843 is about 86.3942150762.

The spelling of 644843 in words is "six hundred forty-four thousand, eight hundred forty-three".