21547222181 has 6 divisors (see below), whose sum is σ = 22524790470. Its totient is φ = 20610385928.

The previous prime is 21547222129. The next prime is 21547222187. The reversal of 21547222181 is 18122274512.

It can be written as a sum of positive squares in only one way, i.e., 17998637281 + 3548584900 = 134159^2 + 59570^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21547222181 is a prime.

It is a super-2 number, since 2×21547222181² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21547222187) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 20365466 + ... + 20366523.

It is an arithmetic number, because the mean of its divisors is an integer number (3754131745).

Almost surely, 2^21547222181 is an apocalyptic number.

It is an amenable number.

21547222181 is a deficient number, since it is larger than the sum of its proper divisors (977568289).

21547222181 is an equidigital number, since it uses as much as digits as its factorization.

21547222181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40732035 (or 40732012 counting only the distinct ones).

The product of its digits is 17920, while the sum is 35.

Adding to 21547222181 its reverse (18122274512), we get a palindrome (39669496693).

The spelling of 21547222181 in words is "twenty-one billion, five hundred forty-seven million, two hundred twenty-two thousand, one hundred eighty-one".