21403231 has 4 divisors (see below), whose sum is σ = 21427200. Its totient is φ = 21379264.

The previous prime is 21403229. The next prime is 21403241. The reversal of 21403231 is 13230412.

It is a happy number.

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 21403231 - 2¹ = 21403229 is a prime.

It is a super-2 number, since 2×21403231² = 916196594478722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21403211) 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, 10591 + ... + 12448.

It is an arithmetic number, because the mean of its divisors is an integer number (5356800).

Almost surely, 2^21403231 is an apocalyptic number.

21403231 is a deficient number, since it is larger than the sum of its proper divisors (23969).

21403231 is an equidigital number, since it uses as much as digits as its factorization.

21403231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23968.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21403231 is about 4626.3626100858. The cubic root of 21403231 is about 277.6470816215.

Adding to 21403231 its reverse (13230412), we get a palindrome (34633643).

The spelling of 21403231 in words is "twenty-one million, four hundred three thousand, two hundred thirty-one".