21808271 has 2 divisors, whose sum is σ = 21808272. Its totient is φ = 21808270.

The previous prime is 21808247. The next prime is 21808291. The reversal of 21808271 is 17280812.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21808271 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21808231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10904135 + 10904136.

It is an arithmetic number, because the mean of its divisors is an integer number (10904136).

Almost surely, 2^21808271 is an apocalyptic number.

21808271 is a deficient number, since it is larger than the sum of its proper divisors (1).

21808271 is an equidigital number, since it uses as much as digits as its factorization.

21808271 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21808271 is about 4669.9326547607. The cubic root of 21808271 is about 279.3875687466.

The spelling of 21808271 in words is "twenty-one million, eight hundred eight thousand, two hundred seventy-one".