21211121 has 8 divisors (see below), whose sum is σ = 22610304. Its totient is φ = 19828800.

The previous prime is 21211109. The next prime is 21211139. The reversal of 21211121 is 12111212.

21211121 = 1109² + 1110² + ... + 1125².

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

It is not a de Polignac number, because 21211121 - 2¹⁰ = 21210097 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21211181) 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, 1565 + ... + 6698.

It is an arithmetic number, because the mean of its divisors is an integer number (2826288).

Almost surely, 2^21211121 is an apocalyptic number.

It is an amenable number.

21211121 is a deficient number, since it is larger than the sum of its proper divisors (1399183).

21211121 is a wasteful number, since it uses less digits than its factorization.

21211121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8431.

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

The square root of 21211121 is about 4605.5532783804. The cubic root of 21211121 is about 276.8138870668.

Adding to 21211121 its reverse (12111212), we get a palindrome (33322333).

Subtracting from 21211121 its reverse (12111212), we obtain a palindrome (9099909).

It can be divided in two parts, 2 and 1211121, that multiplied together give a palindrome (2422242).

The spelling of 21211121 in words is "twenty-one million, two hundred eleven thousand, one hundred twenty-one".