21521124553 has 4 divisors (see below), whose sum is σ = 21531085588. Its totient is φ = 21511163520.

The previous prime is 21521124529. The next prime is 21521124607. The reversal of 21521124553 is 35542112512.

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 16524331209 + 4996793344 = 128547^2 + 70688^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21521124553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521124523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4977276 + ... + 4981597.

It is an arithmetic number, because the mean of its divisors is an integer number (5382771397).

Almost surely, 2^21521124553 is an apocalyptic number.

It is an amenable number.

21521124553 is a deficient number, since it is larger than the sum of its proper divisors (9961035).

21521124553 is an equidigital number, since it uses as much as digits as its factorization.

21521124553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9961034.

The product of its digits is 12000, while the sum is 31.

The spelling of 21521124553 in words is "twenty-one billion, five hundred twenty-one million, one hundred twenty-four thousand, five hundred fifty-three".