21122122121 has 4 divisors (see below), whose sum is σ = 21122964372. Its totient is φ = 21121279872.

The previous prime is 21122122097. The next prime is 21122122123. The reversal of 21122122121 is 12122122112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3483360400 + 17638761721 = 59020^2 + 132811^2 .

It is a cyclic number.

It is not a de Polignac number, because 21122122121 - 2⁶ = 21122122057 is a prime.

It is a super-2 number, since 2×21122122121² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21122122121.

It is not an unprimeable number, because it can be changed into a prime (21122122123) 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, 382316 + ... + 434061.

It is an arithmetic number, because the mean of its divisors is an integer number (5280741093).

Almost surely, 2^21122122121 is an apocalyptic number.

It is an amenable number.

21122122121 is a deficient number, since it is larger than the sum of its proper divisors (842251).

21122122121 is an equidigital number, since it uses as much as digits as its factorization.

21122122121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 842250.

The product of its digits is 64, while the sum is 17.

Adding to 21122122121 its reverse (12122122112), we get a palindrome (33244244233).

Subtracting from 21122122121 its reverse (12122122112), we obtain a palindrome (9000000009).

The spelling of 21122122121 in words is "twenty-one billion, one hundred twenty-two million, one hundred twenty-two thousand, one hundred twenty-one".