21222155 has 4 divisors (see below), whose sum is σ = 25466592. Its totient is φ = 16977720.

The previous prime is 21222143. The next prime is 21222163. The reversal of 21222155 is 55122212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21222155 - 2¹⁰ = 21221131 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2122211 + ... + 2122220.

It is an arithmetic number, because the mean of its divisors is an integer number (6366648).

Almost surely, 2^21222155 is an apocalyptic number.

21222155 is a deficient number, since it is larger than the sum of its proper divisors (4244437).

21222155 is an equidigital number, since it uses as much as digits as its factorization.

21222155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4244436.

The product of its digits is 400, while the sum is 20.

The square root of 21222155 is about 4606.7510243120. The cubic root of 21222155 is about 276.8618781648.

Adding to 21222155 its reverse (55122212), we get a palindrome (76344367).

The spelling of 21222155 in words is "twenty-one million, two hundred twenty-two thousand, one hundred fifty-five".