21039231 has 4 divisors (see below), whose sum is σ = 28052312. Its totient is φ = 14026152.

The previous prime is 21039229. The next prime is 21039233. The reversal of 21039231 is 13293012.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (21039229) and next prime (21039233).

It is not a de Polignac number, because 21039231 - 2¹ = 21039229 is a prime.

It is a super-2 number, since 2×21039231² = 885298482142722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21039198 and 21039207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039233) 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, 3506536 + ... + 3506541.

It is an arithmetic number, because the mean of its divisors is an integer number (7013078).

Almost surely, 2^21039231 is an apocalyptic number.

21039231 is a deficient number, since it is larger than the sum of its proper divisors (7013081).

21039231 is an equidigital number, since it uses as much as digits as its factorization.

21039231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7013080.

The product of its (nonzero) digits is 324, while the sum is 21.

The square root of 21039231 is about 4586.8541507225. The cubic root of 21039231 is about 276.0641129151.

The spelling of 21039231 in words is "twenty-one million, thirty-nine thousand, two hundred thirty-one".