644489 has 2 divisors, whose sum is σ = 644490. Its totient is φ = 644488.

The previous prime is 644447. The next prime is 644491. The reversal of 644489 is 984446.

644489 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 640000 + 4489 = 800^2 + 67^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644489 is a prime.

It is a super-2 number, since 2×644489² = 830732142242, which contains 22 as substring.

Together with 644491, it forms a pair of twin primes.

It is a Chen prime.

It is a d-powerful number, because it can be written as 6⁷ + 4⁶ + 4⁸ + 4⁹ + 8⁵ + 9 .

It is not a weakly prime, because it can be changed into another prime (644089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322244 + 322245.

It is an arithmetic number, because the mean of its divisors is an integer number (322245).

2⁶⁴⁴⁴⁸⁹ is an apocalyptic number.

It is an amenable number.

644489 is a deficient number, since it is larger than the sum of its proper divisors (1).

644489 is an equidigital number, since it uses as much as digits as its factorization.

644489 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27648, while the sum is 35.

The square root of 644489 is about 802.8007224710. The cubic root of 644489 is about 86.3784028809.

It can be divided in two parts, 64 and 4489, that multiplied together give a square (287296 = 536²).

The spelling of 644489 in words is "six hundred forty-four thousand, four hundred eighty-nine".