645947509 has 2 divisors, whose sum is σ = 645947510. Its totient is φ = 645947508.

The previous prime is 645947473. The next prime is 645947539. The reversal of 645947509 is 905749546.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 626100484 + 19847025 = 25022^2 + 4455^2 .

It is a cyclic number.

It is not a de Polignac number, because 645947509 - 2⁷ = 645947381 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645947539) 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, 322973754 + 322973755.

It is an arithmetic number, because the mean of its divisors is an integer number (322973755).

Almost surely, 2^645947509 is an apocalyptic number.

It is an amenable number.

645947509 is a deficient number, since it is larger than the sum of its proper divisors (1).

645947509 is an equidigital number, since it uses as much as digits as its factorization.

645947509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1360800, while the sum is 49.

The square root of 645947509 is about 25415.4974179141. The cubic root of 645947509 is about 864.4351325604.

The spelling of 645947509 in words is "six hundred forty-five million, nine hundred forty-seven thousand, five hundred nine".