21521054123 has 4 divisors (see below), whose sum is σ = 21530249568. Its totient is φ = 21511858680.

The previous prime is 21521054101. The next prime is 21521054131. The reversal of 21521054123 is 32145012512.

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 21521054123 - 2²⁰ = 21520005547 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21521054092 and 21521054101.

It is not an unprimeable number, because it can be changed into a prime (21521044123) 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, 4594211 + ... + 4598892.

It is an arithmetic number, because the mean of its divisors is an integer number (5382562392).

Almost surely, 2^21521054123 is an apocalyptic number.

21521054123 is a deficient number, since it is larger than the sum of its proper divisors (9195445).

21521054123 is an equidigital number, since it uses as much as digits as its factorization.

21521054123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9195444.

The product of its (nonzero) digits is 2400, while the sum is 26.

Adding to 21521054123 its reverse (32145012512), we get a palindrome (53666066635).

The spelling of 21521054123 in words is "twenty-one billion, five hundred twenty-one million, fifty-four thousand, one hundred twenty-three".