166436561260521 has 20 divisors (see below), whose sum is σ = 248639531598612. Its totient is φ = 110952318267648.

The previous prime is 166436561260513. The next prime is 166436561260591. The reversal of 166436561260521 is 125062165634661.

166436561260521 is a `hidden beast` number, since 1 + 6 + 6 + 4 + 3 + 6 + 5 + 6 + 1 + 2 + 605 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 165261591978921 + 1174969281600 = 12855411^2 + 1083960^2 .

It is not a de Polignac number, because 166436561260521 - 2³ = 166436561260513 is a prime.

It is a super-2 number, since 2×166436561260521² (a number of 29 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (166436561260591) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 48222036 + ... + 51558101.

Almost surely, 2^{166436561260521} is an apocalyptic number.

It is an amenable number.

166436561260521 is a deficient number, since it is larger than the sum of its proper divisors (82202970338091).

166436561260521 is an equidigital number, since it uses as much as digits as its factorization.

166436561260521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99800742 (or 99800733 counting only the distinct ones).

The product of its (nonzero) digits is 9331200, while the sum is 54.

The spelling of 166436561260521 in words is "one hundred sixty-six trillion, four hundred thirty-six billion, five hundred sixty-one million, two hundred sixty thousand, five hundred twenty-one".