12211721 has 2 divisors, whose sum is σ = 12211722. Its totient is φ = 12211720.

The previous prime is 12211709. The next prime is 12211723. The reversal of 12211721 is 12711221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9765625 + 2446096 = 3125^2 + 1564^2 .

It is an emirp because it is prime and its reverse (12711221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 12211721 - 2⁶ = 12211657 is a prime.

It is a super-2 number, since 2×12211721² = 298252259563682, which contains 22 as substring.

Together with 12211723, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 12211721.

It is not a weakly prime, because it can be changed into another prime (12211723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6105860 + 6105861.

It is an arithmetic number, because the mean of its divisors is an integer number (6105861).

Almost surely, 2^12211721 is an apocalyptic number.

It is an amenable number.

12211721 is a deficient number, since it is larger than the sum of its proper divisors (1).

12211721 is an equidigital number, since it uses as much as digits as its factorization.

12211721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 56, while the sum is 17.

The square root of 12211721 is about 3494.5272927822. The cubic root of 12211721 is about 230.2814512884.

Adding to 12211721 its reverse (12711221), we get a palindrome (24922942).

Subtracting 12211721 from its reverse (12711221), we obtain a triangular number (499500 = T₉₉₉).

The spelling of 12211721 in words is "twelve million, two hundred eleven thousand, seven hundred twenty-one".