21220231 has 2 divisors, whose sum is σ = 21220232. Its totient is φ = 21220230.

The previous prime is 21220223. The next prime is 21220261. The reversal of 21220231 is 13202212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21220231 - 2³ = 21220223 is a prime.

It is a super-2 number, since 2×21220231² = 900596407386722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21220211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610115 + 10610116.

It is an arithmetic number, because the mean of its divisors is an integer number (10610116).

Almost surely, 2^21220231 is an apocalyptic number.

21220231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220231 is an equidigital number, since it uses as much as digits as its factorization.

21220231 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21220231 is about 4606.5421956170. The cubic root of 21220231 is about 276.8535111484.

Adding to 21220231 its reverse (13202212), we get a palindrome (34422443).

The spelling of 21220231 in words is "twenty-one million, two hundred twenty thousand, two hundred thirty-one".