21004231 has 6 divisors (see below), whose sum is σ = 22312760. Its totient is φ = 19768416.

The previous prime is 21004211. The next prime is 21004237. The reversal of 21004231 is 13240012.

It is not a de Polignac number, because 21004231 - 2¹⁷ = 20873159 is a prime.

It is a super-2 number, since 2×21004231² = 882355439802722, 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 (21004237) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36051 + ... + 36628.

Almost surely, 2^21004231 is an apocalyptic number.

21004231 is a deficient number, since it is larger than the sum of its proper divisors (1308529).

21004231 is an equidigital number, since it uses as much as digits as its factorization.

21004231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72713 (or 72696 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21004231 is about 4583.0373116526. The cubic root of 21004231 is about 275.9109449783.

Adding to 21004231 its reverse (13240012), we get a palindrome (34244243).

The spelling of 21004231 in words is "twenty-one million, four thousand, two hundred thirty-one".