644443823 has 2 divisors, whose sum is σ = 644443824. Its totient is φ = 644443822.

The previous prime is 644443817. The next prime is 644443867. The reversal of 644443823 is 328344446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644443823 - 2⁶ = 644443759 is a prime.

It is a super-3 number, since 3×644443823³ (a number of 27 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644443873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322221911 + 322221912.

It is an arithmetic number, because the mean of its divisors is an integer number (322221912).

Almost surely, 2^644443823 is an apocalyptic number.

644443823 is a deficient number, since it is larger than the sum of its proper divisors (1).

644443823 is an equidigital number, since it uses as much as digits as its factorization.

644443823 is an evil number, because the sum of its binary digits is even.

The product of its digits is 221184, while the sum is 38.

The square root of 644443823 is about 25385.8981129288. The cubic root of 644443823 is about 863.7638453342.

The spelling of 644443823 in words is "six hundred forty-four million, four hundred forty-three thousand, eight hundred twenty-three".