21132123521 has 4 divisors (see below), whose sum is σ = 21137096532. Its totient is φ = 21127150512.

The previous prime is 21132123491. The next prime is 21132123557. The reversal of 21132123521 is 12532123112.

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 9105930625 + 12026192896 = 95425^2 + 109664^2 .

It is a cyclic number.

It is not a de Polignac number, because 21132123521 - 2¹⁰ = 21132122497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21132113521) 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 3 ways as a sum of consecutive naturals, for example, 2480126 + ... + 2488631.

It is an arithmetic number, because the mean of its divisors is an integer number (5284274133).

Almost surely, 2^21132123521 is an apocalyptic number.

It is an amenable number.

21132123521 is a deficient number, since it is larger than the sum of its proper divisors (4973011).

21132123521 is an equidigital number, since it uses as much as digits as its factorization.

21132123521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4973010.

The product of its digits is 720, while the sum is 23.

Adding to 21132123521 its reverse (12532123112), we get a palindrome (33664246633).

The spelling of 21132123521 in words is "twenty-one billion, one hundred thirty-two million, one hundred twenty-three thousand, five hundred twenty-one".