21231121 has 4 divisors (see below), whose sum is σ = 21724912. Its totient is φ = 20737332.

The previous prime is 21231107. The next prime is 21231143. The reversal of 21231121 is 12113212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21231121 - 2¹⁷ = 21100049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21231421) 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, 246831 + ... + 246916.

It is an arithmetic number, because the mean of its divisors is an integer number (5431228).

Almost surely, 2^21231121 is an apocalyptic number.

It is an amenable number.

21231121 is a deficient number, since it is larger than the sum of its proper divisors (493791).

21231121 is an equidigital number, since it uses as much as digits as its factorization.

21231121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 493790.

The product of its digits is 24, while the sum is 13.

The square root of 21231121 is about 4607.7240585782. The cubic root of 21231121 is about 276.9008624888.

Adding to 21231121 its reverse (12113212), we get a palindrome (33344333).

The spelling of 21231121 in words is "twenty-one million, two hundred thirty-one thousand, one hundred twenty-one".