21102121 has 8 divisors (see below), whose sum is σ = 21697280. Its totient is φ = 20511792.

The previous prime is 21102113. The next prime is 21102161. The reversal of 21102121 is 12120112.

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 21102121 - 2³ = 21102113 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21102098 and 21102107.

It is not an unprimeable number, because it can be changed into a prime (21102101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8776 + ... + 10918.

It is an arithmetic number, because the mean of its divisors is an integer number (2712160).

Almost surely, 2^21102121 is an apocalyptic number.

It is an amenable number.

21102121 is a deficient number, since it is larger than the sum of its proper divisors (595159).

21102121 is a wasteful number, since it uses less digits than its factorization.

21102121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2415.

The product of its (nonzero) digits is 8, while the sum is 10.

The square root of 21102121 is about 4593.7044963733. The cubic root of 21102121 is about 276.3389075229.

Adding to 21102121 its reverse (12120112), we get a palindrome (33222233).

Subtracting from 21102121 its reverse (12120112), we obtain a square (8982009 = 2997²).

The spelling of 21102121 in words is "twenty-one million, one hundred two thousand, one hundred twenty-one".