644863 has 2 divisors, whose sum is σ = 644864. Its totient is φ = 644862.

The previous prime is 644857. The next prime is 644867. The reversal of 644863 is 368446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322431 + 322432.

It is an arithmetic number, because the mean of its divisors is an integer number (322432).

2⁶⁴⁴⁸⁶³ is an apocalyptic number.

644863 is a deficient number, since it is larger than the sum of its proper divisors (1).

644863 is an equidigital number, since it uses as much as digits as its factorization.

644863 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13824, while the sum is 31.

The square root of 644863 is about 803.0336232064. The cubic root of 644863 is about 86.3951082479.

The spelling of 644863 in words is "six hundred forty-four thousand, eight hundred sixty-three".