21112121 has 2 divisors, whose sum is σ = 21112122. Its totient is φ = 21112120.

The previous prime is 21112103. The next prime is 21112127. The reversal of 21112121 is 12121112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16000000 + 5112121 = 4000^2 + 2261^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112121 - 2¹⁸ = 20849977 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21112127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10556060 + 10556061.

It is an arithmetic number, because the mean of its divisors is an integer number (10556061).

Almost surely, 2^21112121 is an apocalyptic number.

It is an amenable number.

21112121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112121 is an equidigital number, since it uses as much as digits as its factorization.

21112121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8, while the sum is 11.

The square root of 21112121 is about 4594.7928136098. The cubic root of 21112121 is about 276.3825516773.

Adding to 21112121 its reverse (12121112), we get a palindrome (33233233).

It can be divided in two parts, 21112 and 121, that multiplied together give a palindrome (2554552).

The spelling of 21112121 in words is "twenty-one million, one hundred twelve thousand, one hundred twenty-one".