21547121 has 4 divisors (see below), whose sum is σ = 22681200. Its totient is φ = 20413044.

The previous prime is 21547111. The next prime is 21547129. The reversal of 21547121 is 12174512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21547121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21547129) 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, 567011 + ... + 567048.

It is an arithmetic number, because the mean of its divisors is an integer number (5670300).

Almost surely, 2^21547121 is an apocalyptic number.

It is an amenable number.

21547121 is a deficient number, since it is larger than the sum of its proper divisors (1134079).

21547121 is a wasteful number, since it uses less digits than its factorization.

21547121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1134078.

The product of its digits is 560, while the sum is 23.

The square root of 21547121 is about 4641.8876548232. The cubic root of 21547121 is about 278.2678826665.

The spelling of 21547121 in words is "twenty-one million, five hundred forty-seven thousand, one hundred twenty-one".