11511221 has 4 divisors (see below), whose sum is σ = 11547852. Its totient is φ = 11474592.

The previous prime is 11511217. The next prime is 11511233. The reversal of 11511221 is 12211511.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12211511 = 13 ⋅939347.

It can be written as a sum of positive squares in 2 ways, for example, as 1020100 + 10491121 = 1010^2 + 3239^2 .

It is a cyclic number.

It is not a de Polignac number, because 11511221 - 2² = 11511217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 11511196 and 11511205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11511211) 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, 17840 + ... + 18473.

It is an arithmetic number, because the mean of its divisors is an integer number (2886963).

Almost surely, 2^11511221 is an apocalyptic number.

It is an amenable number.

11511221 is a deficient number, since it is larger than the sum of its proper divisors (36631).

11511221 is an equidigital number, since it uses as much as digits as its factorization.

11511221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36630.

The product of its digits is 20, while the sum is 14.

The square root of 11511221 is about 3392.8190343724. The cubic root of 11511221 is about 225.7912618290.

Adding to 11511221 its reverse (12211511), we get a palindrome (23722732).

The spelling of 11511221 in words is "eleven million, five hundred eleven thousand, two hundred twenty-one".