645136624211581 has 2 divisors, whose sum is σ = 645136624211582. Its totient is φ = 645136624211580.

The previous prime is 645136624211509. The next prime is 645136624211603. The reversal of 645136624211581 is 185112426631546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 493828395062500 + 151308229149081 = 22222250^2 + 12300741^2 .

It is a cyclic number.

It is not a de Polignac number, because 645136624211581 - 2¹¹ = 645136624209533 is a prime.

It is a super-2 number, since 2×645136624211581² (a number of 30 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645136624211501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322568312105790 + 322568312105791.

It is an arithmetic number, because the mean of its divisors is an integer number (322568312105791).

Almost surely, 2^{645136624211581} is an apocalyptic number.

It is an amenable number.

645136624211581 is a deficient number, since it is larger than the sum of its proper divisors (1).

645136624211581 is an equidigital number, since it uses as much as digits as its factorization.

645136624211581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8294400, while the sum is 55.

The spelling of 645136624211581 in words is "six hundred forty-five trillion, one hundred thirty-six billion, six hundred twenty-four million, two hundred eleven thousand, five hundred eighty-one".