21660271 has 2 divisors, whose sum is σ = 21660272. Its totient is φ = 21660270.

The previous prime is 21660269. The next prime is 21660277. The reversal of 21660271 is 17206612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21660271 - 2¹ = 21660269 is a prime.

Together with 21660269, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830135 + 10830136.

It is an arithmetic number, because the mean of its divisors is an integer number (10830136).

Almost surely, 2^21660271 is an apocalyptic number.

21660271 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660271 is an equidigital number, since it uses as much as digits as its factorization.

21660271 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21660271 is about 4654.0596257461. The cubic root of 21660271 is about 278.7541202043.

Adding to 21660271 its reverse (17206612), we get a palindrome (38866883).

The spelling of 21660271 in words is "twenty-one million, six hundred sixty thousand, two hundred seventy-one".