21003231 has 4 divisors (see below), whose sum is σ = 28004312. Its totient is φ = 14002152.

The previous prime is 21003223. The next prime is 21003247. The reversal of 21003231 is 13230012.

It is a happy number.

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

It is not a de Polignac number, because 21003231 - 2³ = 21003223 is a prime.

It is a super-2 number, since 2×21003231² = 882271424878722, 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 (21003271) 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, 3500536 + ... + 3500541.

It is an arithmetic number, because the mean of its divisors is an integer number (7001078).

Almost surely, 2^21003231 is an apocalyptic number.

21003231 is a deficient number, since it is larger than the sum of its proper divisors (7001081).

21003231 is an equidigital number, since it uses as much as digits as its factorization.

21003231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7001080.

The product of its (nonzero) digits is 36, while the sum is 12.

The square root of 21003231 is about 4582.9282123987. The cubic root of 21003231 is about 275.9065662522.

Adding to 21003231 its reverse (13230012), we get a palindrome (34233243).

The spelling of 21003231 in words is "twenty-one million, three thousand, two hundred thirty-one".