645565997 has 2 divisors, whose sum is σ = 645565998. Its totient is φ = 645565996.

The previous prime is 645565967. The next prime is 645566011. The reversal of 645565997 is 799565546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 609793636 + 35772361 = 24694^2 + 5981^2 .

It is a cyclic number.

It is not a de Polignac number, because 645565997 - 2⁶ = 645565933 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645565967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322782998 + 322782999.

It is an arithmetic number, because the mean of its divisors is an integer number (322782999).

Almost surely, 2^645565997 is an apocalyptic number.

It is an amenable number.

645565997 is a deficient number, since it is larger than the sum of its proper divisors (1).

645565997 is an equidigital number, since it uses as much as digits as its factorization.

645565997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10206000, while the sum is 56.

The square root of 645565997 is about 25407.9908099794. The cubic root of 645565997 is about 864.2649137110.

The spelling of 645565997 in words is "six hundred forty-five million, five hundred sixty-five thousand, nine hundred ninety-seven".