21121431 has 4 divisors (see below), whose sum is σ = 28161912. Its totient is φ = 14080952.

The previous prime is 21121417. The next prime is 21121453. The reversal of 21121431 is 13412112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21121431 - 2¹⁴ = 21105047 is a prime.

It is a super-2 number, since 2×21121431² = 892229694975522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21121431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3520236 + ... + 3520241.

It is an arithmetic number, because the mean of its divisors is an integer number (7040478).

Almost surely, 2^21121431 is an apocalyptic number.

21121431 is a deficient number, since it is larger than the sum of its proper divisors (7040481).

21121431 is an equidigital number, since it uses as much as digits as its factorization.

21121431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7040480.

The product of its digits is 48, while the sum is 15.

The square root of 21121431 is about 4595.8058052968. The cubic root of 21121431 is about 276.4231719986.

Adding to 21121431 its reverse (13412112), we get a palindrome (34533543).

The spelling of 21121431 in words is "twenty-one million, one hundred twenty-one thousand, four hundred thirty-one".