12171221 has 4 divisors (see below), whose sum is σ = 12223692. Its totient is φ = 12118752.

The previous prime is 12171199. The next prime is 12171227. The reversal of 12171221 is 12217121.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3556996 + 8614225 = 1886^2 + 2935^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12171221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 12171221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12171227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25886 + ... + 26351.

It is an arithmetic number, because the mean of its divisors is an integer number (3055923).

Almost surely, 2^12171221 is an apocalyptic number.

It is an amenable number.

12171221 is a deficient number, since it is larger than the sum of its proper divisors (52471).

12171221 is an equidigital number, since it uses as much as digits as its factorization.

12171221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52470.

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

The square root of 12171221 is about 3488.7277050524. The cubic root of 12171221 is about 230.0265942784.

Adding to 12171221 its reverse (12217121), we get a palindrome (24388342).

The spelling of 12171221 in words is "twelve million, one hundred seventy-one thousand, two hundred twenty-one".