21355231 has 2 divisors, whose sum is σ = 21355232. Its totient is φ = 21355230.

The previous prime is 21355207. The next prime is 21355241. The reversal of 21355231 is 13255312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21355231 - 2⁵ = 21355199 is a prime.

It is a super-2 number, since 2×21355231² = 912091782126722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21355241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10677615 + 10677616.

It is an arithmetic number, because the mean of its divisors is an integer number (10677616).

Almost surely, 2^21355231 is an apocalyptic number.

21355231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21355231 is an equidigital number, since it uses as much as digits as its factorization.

21355231 is an evil number, because the sum of its binary digits is even.

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

The square root of 21355231 is about 4621.1720374814. The cubic root of 21355231 is about 277.4393710037.

The spelling of 21355231 in words is "twenty-one million, three hundred fifty-five thousand, two hundred thirty-one".