645781589 has 2 divisors, whose sum is σ = 645781590. Its totient is φ = 645781588.

The previous prime is 645781571. The next prime is 645781613. The reversal of 645781589 is 985187546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 578787364 + 66994225 = 24058^2 + 8185^2 .

It is a cyclic number.

It is not a de Polignac number, because 645781589 - 2⁸ = 645781333 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 645781589.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645781559) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322890794 + 322890795.

It is an arithmetic number, because the mean of its divisors is an integer number (322890795).

Almost surely, 2^645781589 is an apocalyptic number.

It is an amenable number.

645781589 is a deficient number, since it is larger than the sum of its proper divisors (1).

645781589 is an equidigital number, since it uses as much as digits as its factorization.

645781589 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2419200, while the sum is 53.

The square root of 645781589 is about 25412.2330581159. The cubic root of 645781589 is about 864.3611124286.

The spelling of 645781589 in words is "six hundred forty-five million, seven hundred eighty-one thousand, five hundred eighty-nine".