21171571 has 2 divisors, whose sum is σ = 21171572. Its totient is φ = 21171570.

The previous prime is 21171551. The next prime is 21171593. The reversal of 21171571 is 17517112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21171571 - 2¹⁷ = 21040499 is a prime.

It is not a weakly prime, because it can be changed into another prime (21171551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10585785 + 10585786.

It is an arithmetic number, because the mean of its divisors is an integer number (10585786).

Almost surely, 2^21171571 is an apocalyptic number.

21171571 is a deficient number, since it is larger than the sum of its proper divisors (1).

21171571 is an equidigital number, since it uses as much as digits as its factorization.

21171571 is an evil number, because the sum of its binary digits is even.

The product of its digits is 490, while the sum is 25.

The square root of 21171571 is about 4601.2575454978. The cubic root of 21171571 is about 276.6417320797.

Adding to 21171571 its reverse (17517112), we get a palindrome (38688683).

The spelling of 21171571 in words is "twenty-one million, one hundred seventy-one thousand, five hundred seventy-one".