21217571 has 2 divisors, whose sum is σ = 21217572. Its totient is φ = 21217570.

The previous prime is 21217561. The next prime is 21217577. The reversal of 21217571 is 17571212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21217571 - 2⁶ = 21217507 is a prime.

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 21217571.

It is not a weakly prime, because it can be changed into another prime (21217577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608785 + 10608786.

It is an arithmetic number, because the mean of its divisors is an integer number (10608786).

Almost surely, 2^21217571 is an apocalyptic number.

21217571 is a deficient number, since it is larger than the sum of its proper divisors (1).

21217571 is an equidigital number, since it uses as much as digits as its factorization.

21217571 is an evil number, because the sum of its binary digits is even.

The product of its digits is 980, while the sum is 26.

The square root of 21217571 is about 4606.2534667558. The cubic root of 21217571 is about 276.8419426110.

Adding to 21217571 its reverse (17571212), we get a palindrome (38788783).

The spelling of 21217571 in words is "twenty-one million, two hundred seventeen thousand, five hundred seventy-one".