21866121 has 12 divisors (see below), whose sum is σ = 32102980. Its totient is φ = 14338080.

The previous prime is 21866113. The next prime is 21866137. The reversal of 21866121 is 12166812.

It can be written as a sum of positive squares in 2 ways, for example, as 10169721 + 11696400 = 3189^2 + 3420^2 .

It is not a de Polignac number, because 21866121 - 2³ = 21866113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21866111) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19366 + ... + 20463.

Almost surely, 2^21866121 is an apocalyptic number.

It is an amenable number.

21866121 is a deficient number, since it is larger than the sum of its proper divisors (10236859).

21866121 is a wasteful number, since it uses less digits than its factorization.

21866121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39896 (or 39893 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 21866121 is about 4676.1224321012. The cubic root of 21866121 is about 279.6343910124.

The spelling of 21866121 in words is "twenty-one million, eight hundred sixty-six thousand, one hundred twenty-one".