21101112121 has 4 divisors (see below), whose sum is σ = 21101409252. Its totient is φ = 21100814992.

The previous prime is 21101112119. The next prime is 21101112127. The reversal of 21101112121 is 12121110112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 8660163600 + 12440948521 = 93060^2 + 111539^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101112121 - 2¹ = 21101112119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21101112127) 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, 27555 + ... + 207271.

It is an arithmetic number, because the mean of its divisors is an integer number (5275352313).

Almost surely, 2^21101112121 is an apocalyptic number.

It is an amenable number.

21101112121 is a deficient number, since it is larger than the sum of its proper divisors (297131).

21101112121 is a wasteful number, since it uses less digits than its factorization.

21101112121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 297130.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21101112121 its reverse (12121110112), we get a palindrome (33222222233).

The spelling of 21101112121 in words is "twenty-one billion, one hundred one million, one hundred twelve thousand, one hundred twenty-one".