21031121 has 4 divisors (see below), whose sum is σ = 21284592. Its totient is φ = 20777652.

The previous prime is 21031111. The next prime is 21031151. The reversal of 21031121 is 12113012.

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 a de Polignac number, because none of the positive numbers 2^k-21031121 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 (21031111) 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, 126611 + ... + 126776.

It is an arithmetic number, because the mean of its divisors is an integer number (5321148).

Almost surely, 2^21031121 is an apocalyptic number.

It is an amenable number.

21031121 is a deficient number, since it is larger than the sum of its proper divisors (253471).

21031121 is an equidigital number, since it uses as much as digits as its factorization.

21031121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253470.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21031121 is about 4585.9700173464. The cubic root of 21031121 is about 276.0286368452.

Adding to 21031121 its reverse (12113012), we get a palindrome (33144133).

The spelling of 21031121 in words is "twenty-one million, thirty-one thousand, one hundred twenty-one".