645376673549 has 2 divisors, whose sum is σ = 645376673550. Its totient is φ = 645376673548.

The previous prime is 645376673527. The next prime is 645376673573. The reversal of 645376673549 is 945376673546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 567475956100 + 77900717449 = 753310^2 + 279107^2 .

It is a cyclic number.

It is not a de Polignac number, because 645376673549 - 2¹⁶ = 645376608013 is a prime.

It is a super-2 number, since 2×645376673549² (a number of 24 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645376673449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322688336774 + 322688336775.

It is an arithmetic number, because the mean of its divisors is an integer number (322688336775).

Almost surely, 2^645376673549 is an apocalyptic number.

It is an amenable number.

645376673549 is a deficient number, since it is larger than the sum of its proper divisors (1).

645376673549 is an equidigital number, since it uses as much as digits as its factorization.

645376673549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 342921600, while the sum is 65.

The spelling of 645376673549 in words is "six hundred forty-five billion, three hundred seventy-six million, six hundred seventy-three thousand, five hundred forty-nine".