21655312173 has 48 divisors (see below), whose sum is σ = 36210510336. Its totient is φ = 12819144240.

The previous prime is 21655312141. The next prime is 21655312183. The reversal of 21655312173 is 37121355612.

21655312173 is a `hidden beast` number, since 2 + 16 + 553 + 1 + 21 + 73 = 666.

It is not a de Polignac number, because 21655312173 - 2⁵ = 21655312141 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655312183) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 20736 + ... + 209142.

It is an arithmetic number, because the mean of its divisors is an integer number (754385632).

Almost surely, 2^21655312173 is an apocalyptic number.

It is an amenable number.

21655312173 is a deficient number, since it is larger than the sum of its proper divisors (14555198163).

21655312173 is a wasteful number, since it uses less digits than its factorization.

21655312173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188476 (or 188464 counting only the distinct ones).

The product of its digits is 37800, while the sum is 36.

Adding to 21655312173 its reverse (37121355612), we get a palindrome (58776667785).

The spelling of 21655312173 in words is "twenty-one billion, six hundred fifty-five million, three hundred twelve thousand, one hundred seventy-three".