644323543 has 2 divisors, whose sum is σ = 644323544. Its totient is φ = 644323542.

The previous prime is 644323453. The next prime is 644323549. The reversal of 644323543 is 345323446.

Together with previous prime (644323453) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644323543 is a prime.

It is a super-3 number, since 3×644323543³ (a number of 27 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644323499 and 644323508.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644323549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322161771 + 322161772.

It is an arithmetic number, because the mean of its divisors is an integer number (322161772).

Almost surely, 2^644323543 is an apocalyptic number.

644323543 is a deficient number, since it is larger than the sum of its proper divisors (1).

644323543 is an equidigital number, since it uses as much as digits as its factorization.

644323543 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 103680, while the sum is 34.

The square root of 644323543 is about 25383.5289705746. The cubic root of 644323543 is about 863.7101039136.

Adding to 644323543 its reverse (345323446), we get a palindrome (989646989).

The spelling of 644323543 in words is "six hundred forty-four million, three hundred twenty-three thousand, five hundred forty-three".