21535231 has 2 divisors, whose sum is σ = 21535232. Its totient is φ = 21535230.

The previous prime is 21535187. The next prime is 21535237. The reversal of 21535231 is 13253512.

21535231 is nontrivially palindromic in base 12.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21535231 - 2¹⁵ = 21502463 is a prime.

It is a super-2 number, since 2×21535231² = 927532348446722, which contains 22 as substring.

It is a Chen prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21535237) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767615 + 10767616.

It is an arithmetic number, because the mean of its divisors is an integer number (10767616).

Almost surely, 2^21535231 is an apocalyptic number.

21535231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21535231 is an equidigital number, since it uses as much as digits as its factorization.

21535231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 900, while the sum is 22.

The square root of 21535231 is about 4640.6067491224. The cubic root of 21535231 is about 278.2166892242.

Adding to 21535231 its reverse (13253512), we get a palindrome (34788743).

The spelling of 21535231 in words is "twenty-one million, five hundred thirty-five thousand, two hundred thirty-one".