21566121 has 8 divisors (see below), whose sum is σ = 30268320. Its totient is φ = 13620672.

The previous prime is 21566119. The next prime is 21566141. The reversal of 21566121 is 12166512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21566121 - 2¹ = 21566119 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21566091 and 21566100.

It is not an unprimeable number, because it can be changed into a prime (21566101) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 189120 + ... + 189233.

It is an arithmetic number, because the mean of its divisors is an integer number (3783540).

Almost surely, 2^21566121 is an apocalyptic number.

It is an amenable number.

21566121 is a deficient number, since it is larger than the sum of its proper divisors (8702199).

21566121 is a wasteful number, since it uses less digits than its factorization.

21566121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 378375.

The product of its digits is 720, while the sum is 24.

The square root of 21566121 is about 4643.9337850577. The cubic root of 21566121 is about 278.3496497620.

The spelling of 21566121 in words is "twenty-one million, five hundred sixty-six thousand, one hundred twenty-one".