21247271 has 2 divisors, whose sum is σ = 21247272. Its totient is φ = 21247270.

The previous prime is 21247267. The next prime is 21247273. The reversal of 21247271 is 17274212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21247271 - 2² = 21247267 is a prime.

Together with 21247273, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21247271.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21247273) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10623635 + 10623636.

It is an arithmetic number, because the mean of its divisors is an integer number (10623636).

Almost surely, 2^21247271 is an apocalyptic number.

21247271 is a deficient number, since it is larger than the sum of its proper divisors (1).

21247271 is an equidigital number, since it uses as much as digits as its factorization.

21247271 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1568, while the sum is 26.

The square root of 21247271 is about 4609.4762175327. The cubic root of 21247271 is about 276.9710552890.

The spelling of 21247271 in words is "twenty-one million, two hundred forty-seven thousand, two hundred seventy-one".