21222181 has 2 divisors, whose sum is σ = 21222182. Its totient is φ = 21222180.

The previous prime is 21222163. The next prime is 21222211. The reversal of 21222181 is 18122212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19936225 + 1285956 = 4465^2 + 1134^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21222181 is a prime.

It is a super-2 number, since 2×21222181² = 900761932793522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21226181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10611090 + 10611091.

It is an arithmetic number, because the mean of its divisors is an integer number (10611091).

Almost surely, 2^21222181 is an apocalyptic number.

It is an amenable number.

21222181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21222181 is an equidigital number, since it uses as much as digits as its factorization.

21222181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 128, while the sum is 19.

The square root of 21222181 is about 4606.7538462566. The cubic root of 21222181 is about 276.8619912291.

Adding to 21222181 its reverse (18122212), we get a palindrome (39344393).

The spelling of 21222181 in words is "twenty-one million, two hundred twenty-two thousand, one hundred eighty-one".