644663473 has 2 divisors, whose sum is σ = 644663474. Its totient is φ = 644663472.

The previous prime is 644663419. The next prime is 644663489. The reversal of 644663473 is 374366446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 574656784 + 70006689 = 23972^2 + 8367^2 .

It is a cyclic number.

It is not a de Polignac number, because 644663473 - 2⁹ = 644662961 is a prime.

It is not a weakly prime, because it can be changed into another prime (644663413) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322331736 + 322331737.

It is an arithmetic number, because the mean of its divisors is an integer number (322331737).

Almost surely, 2^644663473 is an apocalyptic number.

It is an amenable number.

644663473 is a deficient number, since it is larger than the sum of its proper divisors (1).

644663473 is an equidigital number, since it uses as much as digits as its factorization.

644663473 is an evil number, because the sum of its binary digits is even.

The product of its digits is 870912, while the sum is 43.

The square root of 644663473 is about 25390.2239651406. The cubic root of 644663473 is about 863.8619682793.

The spelling of 644663473 in words is "six hundred forty-four million, six hundred sixty-three thousand, four hundred seventy-three".