644647 has 2 divisors, whose sum is σ = 644648. Its totient is φ = 644646.

The previous prime is 644629. The next prime is 644653. The reversal of 644647 is 746446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644647 - 2⁷ = 644519 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644617) 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, 322323 + 322324.

It is an arithmetic number, because the mean of its divisors is an integer number (322324).

2⁶⁴⁴⁶⁴⁷ is an apocalyptic number.

644647 is a deficient number, since it is larger than the sum of its proper divisors (1).

644647 is an equidigital number, since it uses as much as digits as its factorization.

644647 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16128, while the sum is 31.

The square root of 644647 is about 802.8991219325. The cubic root of 644647 is about 86.3854610167.

The spelling of 644647 in words is "six hundred forty-four thousand, six hundred forty-seven".