21508271 has 2 divisors, whose sum is σ = 21508272. Its totient is φ = 21508270.

The previous prime is 21508261. The next prime is 21508297. The reversal of 21508271 is 17280512.

It is an a-pointer prime, because the next prime (21508297) can be obtained adding 21508271 to its sum of digits (26).

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21508271 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21508271.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21508241) 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, 10754135 + 10754136.

It is an arithmetic number, because the mean of its divisors is an integer number (10754136).

Almost surely, 2^21508271 is an apocalyptic number.

21508271 is a deficient number, since it is larger than the sum of its proper divisors (1).

21508271 is an equidigital number, since it uses as much as digits as its factorization.

21508271 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21508271 is about 4637.7010468550. The cubic root of 21508271 is about 278.1005407266.

Adding to 21508271 its reverse (17280512), we get a palindrome (38788783).

The spelling of 21508271 in words is "twenty-one million, five hundred eight thousand, two hundred seventy-one".