645889929988561 has 2 divisors, whose sum is σ = 645889929988562. Its totient is φ = 645889929988560.

The previous prime is 645889929988507. The next prime is 645889929988579. The reversal of 645889929988561 is 165889929988546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 484612629738561 + 161277300250000 = 22013919^2 + 12699500^2 .

It is a cyclic number.

It is not a de Polignac number, because 645889929988561 - 2²³ = 645889921599953 is a prime.

It is not a weakly prime, because it can be changed into another prime (645889929989561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322944964994280 + 322944964994281.

It is an arithmetic number, because the mean of its divisors is an integer number (322944964994281).

Almost surely, 2^{645889929988561} is an apocalyptic number.

It is an amenable number.

645889929988561 is a deficient number, since it is larger than the sum of its proper divisors (1).

645889929988561 is an equidigital number, since it uses as much as digits as its factorization.

645889929988561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193491763200, while the sum is 97.

The spelling of 645889929988561 in words is "six hundred forty-five trillion, eight hundred eighty-nine billion, nine hundred twenty-nine million, nine hundred eighty-eight thousand, five hundred sixty-one".