21122111212121 has 8 divisors (see below), whose sum is σ = 21146940766344. Its totient is φ = 21097283356800.

The previous prime is 21122111212043. The next prime is 21122111212201. The reversal of 21122111212121 is 12121211122112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 7252922265625 + 13869188946496 = 2693125^2 + 3724136^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21122111212121 is a prime.

It is a super-3 number, since 3×21122111212121³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21122111212093 and 21122111212102.

It is not an unprimeable number, because it can be changed into a prime (21122111211121) 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, 25375091 + ... + 26194263.

It is an arithmetic number, because the mean of its divisors is an integer number (2643367595793).

Almost surely, 2^{21122111212121} is an apocalyptic number.

It is an amenable number.

21122111212121 is a deficient number, since it is larger than the sum of its proper divisors (24829554223).

21122111212121 is an equidigital number, since it uses as much as digits as its factorization.

21122111212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 849451.

The product of its digits is 64, while the sum is 20.

Adding to 21122111212121 its reverse (12121211122112), we get a palindrome (33243322334233).

Subtracting from 21122111212121 its reverse (12121211122112), we obtain a palindrome (9000900090009).

The spelling of 21122111212121 in words is "twenty-one trillion, one hundred twenty-two billion, one hundred eleven million, two hundred twelve thousand, one hundred twenty-one".