644923 has 2 divisors, whose sum is σ = 644924. Its totient is φ = 644922.

The previous prime is 644911. The next prime is 644933. The reversal of 644923 is 329446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644923 - 2⁹ = 644411 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644891 and 644900.

It is not a weakly prime, because it can be changed into another prime (644933) 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, 322461 + 322462.

It is an arithmetic number, because the mean of its divisors is an integer number (322462).

2⁶⁴⁴⁹²³ is an apocalyptic number.

644923 is a deficient number, since it is larger than the sum of its proper divisors (1).

644923 is an equidigital number, since it uses as much as digits as its factorization.

644923 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 28.

The square root of 644923 is about 803.0709806736. The cubic root of 644923 is about 86.3977876520.

The spelling of 644923 in words is "six hundred forty-four thousand, nine hundred twenty-three".