644505481 has 2 divisors, whose sum is σ = 644505482. Its totient is φ = 644505480.

The previous prime is 644505427. The next prime is 644505487. The reversal of 644505481 is 184505446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 407838025 + 236667456 = 20195^2 + 15384^2 .

It is a cyclic number.

It is not a de Polignac number, because 644505481 - 2⁷ = 644505353 is a prime.

It is a super-2 number, since 2×644505481² = 830774630078082722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 644505481.

It is not a weakly prime, because it can be changed into another prime (644505487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322252740 + 322252741.

It is an arithmetic number, because the mean of its divisors is an integer number (322252741).

Almost surely, 2^644505481 is an apocalyptic number.

It is an amenable number.

644505481 is a deficient number, since it is larger than the sum of its proper divisors (1).

644505481 is an equidigital number, since it uses as much as digits as its factorization.

644505481 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 76800, while the sum is 37.

The square root of 644505481 is about 25387.1124982736. The cubic root of 644505481 is about 863.7913916984.

The spelling of 644505481 in words is "six hundred forty-four million, five hundred five thousand, four hundred eighty-one".