644653 has 2 divisors, whose sum is σ = 644654. Its totient is φ = 644652.

The previous prime is 644647. The next prime is 644669. The reversal of 644653 is 356446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 580644 + 64009 = 762^2 + 253^2 .

It is a cyclic number.

It is not a de Polignac number, because 644653 - 2⁹ = 644141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644053) 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, 322326 + 322327.

It is an arithmetic number, because the mean of its divisors is an integer number (322327).

2⁶⁴⁴⁶⁵³ is an apocalyptic number.

It is an amenable number.

644653 is a deficient number, since it is larger than the sum of its proper divisors (1).

644653 is an equidigital number, since it uses as much as digits as its factorization.

644653 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8640, while the sum is 28.

The square root of 644653 is about 802.9028583833. The cubic root of 644653 is about 86.3857290244.

It can be divided in two parts, 64 and 4653, that multiplied together give a palindrome (297792).

The spelling of 644653 in words is "six hundred forty-four thousand, six hundred fifty-three".