645765121 has 2 divisors, whose sum is σ = 645765122. Its totient is φ = 645765120.

The previous prime is 645765073. The next prime is 645765137. The reversal of 645765121 is 121567546.

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., 621804096 + 23961025 = 24936^2 + 4895^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645765121 is a prime.

It is not a weakly prime, because it can be changed into another prime (645765151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322882560 + 322882561.

It is an arithmetic number, because the mean of its divisors is an integer number (322882561).

Almost surely, 2^645765121 is an apocalyptic number.

It is an amenable number.

645765121 is a deficient number, since it is larger than the sum of its proper divisors (1).

645765121 is an equidigital number, since it uses as much as digits as its factorization.

645765121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 50400, while the sum is 37.

The square root of 645765121 is about 25411.9090388739. The cubic root of 645765121 is about 864.3537650426.

The spelling of 645765121 in words is "six hundred forty-five million, seven hundred sixty-five thousand, one hundred twenty-one".