645520515181 has 2 divisors, whose sum is σ = 645520515182. Its totient is φ = 645520515180.

The previous prime is 645520515121. The next prime is 645520515193. The reversal of 645520515181 is 181515025546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 435329442025 + 210191073156 = 659795^2 + 458466^2 .

It is a cyclic number.

It is not a de Polignac number, because 645520515181 - 2⁷ = 645520515053 is a prime.

It is a super-2 number, since 2×645520515181² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645520515121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322760257590 + 322760257591.

It is an arithmetic number, because the mean of its divisors is an integer number (322760257591).

Almost surely, 2^645520515181 is an apocalyptic number.

It is an amenable number.

645520515181 is a deficient number, since it is larger than the sum of its proper divisors (1).

645520515181 is an equidigital number, since it uses as much as digits as its factorization.

645520515181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 240000, while the sum is 43.

The spelling of 645520515181 in words is "six hundred forty-five billion, five hundred twenty million, five hundred fifteen thousand, one hundred eighty-one".