21821171 has 2 divisors, whose sum is σ = 21821172. Its totient is φ = 21821170.

The previous prime is 21821153. The next prime is 21821197. The reversal of 21821171 is 17112812.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21821171 is a prime.

It is a super-2 number, since 2×21821171² = 952327007622482, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21821141) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10910585 + 10910586.

It is an arithmetic number, because the mean of its divisors is an integer number (10910586).

Almost surely, 2^21821171 is an apocalyptic number.

21821171 is a deficient number, since it is larger than the sum of its proper divisors (1).

21821171 is an equidigital number, since it uses as much as digits as its factorization.

21821171 is an evil number, because the sum of its binary digits is even.

The product of its digits is 224, while the sum is 23.

The square root of 21821171 is about 4671.3136268078. The cubic root of 21821171 is about 279.4426455450.

Adding to 21821171 its reverse (17112812), we get a palindrome (38933983).

The spelling of 21821171 in words is "twenty-one million, eight hundred twenty-one thousand, one hundred seventy-one".