644747 has 2 divisors, whose sum is σ = 644748. Its totient is φ = 644746.

The previous prime is 644731. The next prime is 644753. The reversal of 644747 is 747446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644747 - 2⁴ = 644731 is a prime.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644747.

It is not a weakly prime, because it can be changed into another prime (644717) 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, 322373 + 322374.

It is an arithmetic number, because the mean of its divisors is an integer number (322374).

2⁶⁴⁴⁷⁴⁷ is an apocalyptic number.

644747 is a deficient number, since it is larger than the sum of its proper divisors (1).

644747 is an equidigital number, since it uses as much as digits as its factorization.

644747 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18816, while the sum is 32.

The square root of 644747 is about 802.9613938416. The cubic root of 644747 is about 86.3899275953.

The spelling of 644747 in words is "six hundred forty-four thousand, seven hundred forty-seven".