21330431 has 4 divisors (see below), whose sum is σ = 21340152. Its totient is φ = 21320712.

The previous prime is 21330403. The next prime is 21330443. The reversal of 21330431 is 13403312.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21330431 - 2⁶ = 21330367 is a prime.

It is a super-2 number, since 2×21330431² = 909974573291522, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21330481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 161 + ... + 6533.

It is an arithmetic number, because the mean of its divisors is an integer number (5335038).

Almost surely, 2^21330431 is an apocalyptic number.

21330431 is a deficient number, since it is larger than the sum of its proper divisors (9721).

21330431 is an equidigital number, since it uses as much as digits as its factorization.

21330431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9720.

The product of its (nonzero) digits is 216, while the sum is 17.

The square root of 21330431 is about 4618.4879560306. The cubic root of 21330431 is about 277.3319318852.

Adding to 21330431 its reverse (13403312), we get a palindrome (34733743).

The spelling of 21330431 in words is "twenty-one million, three hundred thirty thousand, four hundred thirty-one".