21572231 has 2 divisors, whose sum is σ = 21572232. Its totient is φ = 21572230.

The previous prime is 21572227. The next prime is 21572233. The reversal of 21572231 is 13227512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21572231 - 2² = 21572227 is a prime.

It is a super-2 number, since 2×21572231² = 930722300634722, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21572233, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21572197 and 21572206.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21572233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10786115 + 10786116.

It is an arithmetic number, because the mean of its divisors is an integer number (10786116).

Almost surely, 2^21572231 is an apocalyptic number.

21572231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21572231 is an equidigital number, since it uses as much as digits as its factorization.

21572231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 840, while the sum is 23.

The square root of 21572231 is about 4644.5915859201. The cubic root of 21572231 is about 278.3759341329.

Adding to 21572231 its reverse (13227512), we get a palindrome (34799743).

The spelling of 21572231 in words is "twenty-one million, five hundred seventy-two thousand, two hundred thirty-one".