168121538821 has 4 divisors (see below), whose sum is σ = 168658668652. Its totient is φ = 167584408992.

The previous prime is 168121538807. The next prime is 168121538869. The reversal of 168121538821 is 128835121861.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18793393921 + 149328144900 = 137089^2 + 386430^2 .

It is a cyclic number.

It is not a de Polignac number, because 168121538821 - 2¹⁵ = 168121506053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (168121538881) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 268564446 + ... + 268565071.

It is an arithmetic number, because the mean of its divisors is an integer number (42164667163).

Almost surely, 2^168121538821 is an apocalyptic number.

It is an amenable number.

168121538821 is a deficient number, since it is larger than the sum of its proper divisors (537129831).

168121538821 is an equidigital number, since it uses as much as digits as its factorization.

168121538821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 537129830.

The product of its digits is 184320, while the sum is 46.

The spelling of 168121538821 in words is "one hundred sixty-eight billion, one hundred twenty-one million, five hundred thirty-eight thousand, eight hundred twenty-one".