21222122221 has 8 divisors (see below), whose sum is σ = 21553250840. Its totient is φ = 20893474368.

The previous prime is 21222122209. The next prime is 21222122239. The reversal of 21222122221 is 12222122212.

It can be written as a sum of positive squares in 4 ways, for example, as 702992196 + 20519130025 = 26514^2 + 143245^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21222122221 - 2⁷ = 21222122093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21222122281) 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, 602946 + ... + 637171.

It is an arithmetic number, because the mean of its divisors is an integer number (2694156355).

Almost surely, 2^21222122221 is an apocalyptic number.

It is an amenable number.

21222122221 is a deficient number, since it is larger than the sum of its proper divisors (331128619).

21222122221 is a wasteful number, since it uses less digits than its factorization.

21222122221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1240383.

The product of its digits is 256, while the sum is 19.

Adding to 21222122221 its reverse (12222122212), we get a palindrome (33444244433).

Subtracting from 21222122221 its reverse (12222122212), we obtain a palindrome (9000000009).

The spelling of 21222122221 in words is "twenty-one billion, two hundred twenty-two million, one hundred twenty-two thousand, two hundred twenty-one".