645323551 has 2 divisors, whose sum is σ = 645323552. Its totient is φ = 645323550.

The previous prime is 645323521. The next prime is 645323561. The reversal of 645323551 is 155323546.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645323551 - 2²³ = 636934943 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645323501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322661775 + 322661776.

It is an arithmetic number, because the mean of its divisors is an integer number (322661776).

Almost surely, 2^645323551 is an apocalyptic number.

645323551 is a deficient number, since it is larger than the sum of its proper divisors (1).

645323551 is an equidigital number, since it uses as much as digits as its factorization.

645323551 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54000, while the sum is 34.

The square root of 645323551 is about 25403.2193038599. The cubic root of 645323551 is about 864.1567069545.

The spelling of 645323551 in words is "six hundred forty-five million, three hundred twenty-three thousand, five hundred fifty-one".