644899 has 2 divisors, whose sum is σ = 644900. Its totient is φ = 644898.

The previous prime is 644881. The next prime is 644909. The reversal of 644899 is 998446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644899 - 2⁵ = 644867 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322449 + 322450.

It is an arithmetic number, because the mean of its divisors is an integer number (322450).

2⁶⁴⁴⁸⁹⁹ is an apocalyptic number.

644899 is a deficient number, since it is larger than the sum of its proper divisors (1).

644899 is an equidigital number, since it uses as much as digits as its factorization.

644899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 40.

The square root of 644899 is about 803.0560378952. The cubic root of 644899 is about 86.3967159103.

The spelling of 644899 in words is "six hundred forty-four thousand, eight hundred ninety-nine".