644211653 has 2 divisors, whose sum is σ = 644211654. Its totient is φ = 644211652.

The previous prime is 644211643. The next prime is 644211677. The reversal of 644211653 is 356112446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 605061604 + 39150049 = 24598^2 + 6257^2 .

It is a cyclic number.

It is not a de Polignac number, because 644211653 - 2¹⁰ = 644210629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644211643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322105826 + 322105827.

It is an arithmetic number, because the mean of its divisors is an integer number (322105827).

Almost surely, 2^644211653 is an apocalyptic number.

It is an amenable number.

644211653 is a deficient number, since it is larger than the sum of its proper divisors (1).

644211653 is an equidigital number, since it uses as much as digits as its factorization.

644211653 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17280, while the sum is 32.

The square root of 644211653 is about 25381.3248866169. The cubic root of 644211653 is about 863.6601051622.

The spelling of 644211653 in words is "six hundred forty-four million, two hundred eleven thousand, six hundred fifty-three".