21547621523 has 4 divisors (see below), whose sum is σ = 21789729720. Its totient is φ = 21305513328.

The previous prime is 21547621471. The next prime is 21547621531. The reversal of 21547621523 is 32512674512.

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 21547621523 - 2¹⁰ = 21547620499 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21547621723) 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, 121053965 + ... + 121054142.

It is an arithmetic number, because the mean of its divisors is an integer number (5447432430).

Almost surely, 2^21547621523 is an apocalyptic number.

21547621523 is a deficient number, since it is larger than the sum of its proper divisors (242108197).

21547621523 is an equidigital number, since it uses as much as digits as its factorization.

21547621523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242108196.

The product of its digits is 100800, while the sum is 38.

The spelling of 21547621523 in words is "twenty-one billion, five hundred forty-seven million, six hundred twenty-one thousand, five hundred twenty-three".