21355525161 has 12 divisors (see below), whose sum is σ = 31428886788. Its totient is φ = 13968393504.

The previous prime is 21355525111. The next prime is 21355525181. The reversal of 21355525161 is 16152555312.

21355525161 is a `hidden beast` number, since 2 + 135 + 5 + 5 + 2 + 516 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 8933085225 + 12422439936 = 94515^2 + 111456^2 .

It is not a de Polignac number, because 21355525161 - 2¹⁹ = 21355000873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21355525111) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22384770 + ... + 22385723.

It is an arithmetic number, because the mean of its divisors is an integer number (2619073899).

Almost surely, 2^21355525161 is an apocalyptic number.

It is an amenable number.

21355525161 is a deficient number, since it is larger than the sum of its proper divisors (10073361627).

21355525161 is a wasteful number, since it uses less digits than its factorization.

21355525161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44770552 (or 44770549 counting only the distinct ones).

The product of its digits is 45000, while the sum is 36.

It can be divided in two parts, 213555251 and 61, that added together give a palindrome (213555312).

The spelling of 21355525161 in words is "twenty-one billion, three hundred fifty-five million, five hundred twenty-five thousand, one hundred sixty-one".