21540174165 has 12 divisors (see below), whose sum is σ = 37336301964. Its totient is φ = 11488092864.

The previous prime is 21540174127. The next prime is 21540174197. The reversal of 21540174165 is 56147104512.

21540174165 is a `hidden beast` number, since 2 + 1 + 540 + 17 + 41 + 65 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 11474265924 + 10065908241 = 107118^2 + 100329^2 .

It is not a de Polignac number, because 21540174165 - 2¹⁷ = 21540043093 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 239335224 + ... + 239335313.

It is an arithmetic number, because the mean of its divisors is an integer number (3111358497).

Almost surely, 2^21540174165 is an apocalyptic number.

It is an amenable number.

21540174165 is a deficient number, since it is larger than the sum of its proper divisors (15796127799).

21540174165 is a wasteful number, since it uses less digits than its factorization.

21540174165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 478670548 (or 478670545 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

Adding to 21540174165 its reverse (56147104512), we get a palindrome (77687278677).

The spelling of 21540174165 in words is "twenty-one billion, five hundred forty million, one hundred seventy-four thousand, one hundred sixty-five".