645691019 has 2 divisors, whose sum is σ = 645691020. Its totient is φ = 645691018.

The previous prime is 645690979. The next prime is 645691021. The reversal of 645691019 is 910196546.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645691019 - 2²⁸ = 377255563 is a prime.

It is a super-2 number, since 2×645691019² = 833833784034516722, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 645691021, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (645691819) 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, 322845509 + 322845510.

It is an arithmetic number, because the mean of its divisors is an integer number (322845510).

Almost surely, 2^645691019 is an apocalyptic number.

645691019 is a deficient number, since it is larger than the sum of its proper divisors (1).

645691019 is an equidigital number, since it uses as much as digits as its factorization.

645691019 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 58320, while the sum is 41.

The square root of 645691019 is about 25410.4509798626. The cubic root of 645691019 is about 864.3207020445.

The spelling of 645691019 in words is "six hundred forty-five million, six hundred ninety-one thousand, nineteen".