644669 has 2 divisors, whose sum is σ = 644670. Its totient is φ = 644668.

The previous prime is 644653. The next prime is 644671. The reversal of 644669 is 966446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 582169 + 62500 = 763^2 + 250^2 .

It is a cyclic number.

It is not a de Polignac number, because 644669 - 2⁴ = 644653 is a prime.

It is a super-2 number, since 2×644669² = 831196239122, which contains 22 as substring.

Together with 644671, it forms a pair of twin primes.

It is a Chen prime.

It is a d-powerful number, because it can be written as 6 + 4⁵ + 6 + 4⁸ + 6⁶ + 9⁶ .

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322334 + 322335.

It is an arithmetic number, because the mean of its divisors is an integer number (322335).

2⁶⁴⁴⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

644669 is a deficient number, since it is larger than the sum of its proper divisors (1).

644669 is an equidigital number, since it uses as much as digits as its factorization.

644669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 35.

The square root of 644669 is about 802.9128221669. The cubic root of 644669 is about 86.3864437036.

The spelling of 644669 in words is "six hundred forty-four thousand, six hundred sixty-nine".