21500231 has 2 divisors, whose sum is σ = 21500232. Its totient is φ = 21500230.

The previous prime is 21500209. The next prime is 21500251. The reversal of 21500231 is 13200512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21500231 - 2²² = 17305927 is a prime.

It is a super-2 number, since 2×21500231² = 924519866106722, 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 (21500251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750115 + 10750116.

It is an arithmetic number, because the mean of its divisors is an integer number (10750116).

Almost surely, 2^21500231 is an apocalyptic number.

21500231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21500231 is an equidigital number, since it uses as much as digits as its factorization.

21500231 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21500231 is about 4636.8341570516. The cubic root of 21500231 is about 278.0658841828.

Adding to 21500231 its reverse (13200512), we get a palindrome (34700743).

The spelling of 21500231 in words is "twenty-one million, five hundred thousand, two hundred thirty-one".