21513533121123 has 4 divisors (see below), whose sum is σ = 28684710828168. Its totient is φ = 14342355414080.

The previous prime is 21513533121103. The next prime is 21513533121193. The reversal of 21513533121123 is 32112133531512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21513533121123 - 2²⁸ = 21513264685667 is a prime.

It is a super-2 number, since 2×21513533121123² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21513533121103) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3585588853518 + ... + 3585588853523.

It is an arithmetic number, because the mean of its divisors is an integer number (7171177707042).

Almost surely, 2^{21513533121123} is an apocalyptic number.

21513533121123 is a deficient number, since it is larger than the sum of its proper divisors (7171177707045).

21513533121123 is an equidigital number, since it uses as much as digits as its factorization.

21513533121123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7171177707044.

The product of its digits is 16200, while the sum is 33.

Adding to 21513533121123 its reverse (32112133531512), we get a palindrome (53625666652635).

The spelling of 21513533121123 in words is "twenty-one trillion, five hundred thirteen billion, five hundred thirty-three million, one hundred twenty-one thousand, one hundred twenty-three".