11551221 has 64 divisors (see below), whose sum is σ = 20736000. Its totient is φ = 6272640.

The previous prime is 11551213. The next prime is 11551229. The reversal of 11551221 is 12215511.

11551221 is a nontrivial binomial coefficient, being equal to C(4807, 2).

It is an interprime number because it is at equal distance from previous prime (11551213) and next prime (11551229).

It is not a de Polignac number, because 11551221 - 2³ = 11551213 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 11551194 and 11551203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11551229) 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 in 63 ways as a sum of consecutive naturals, for example, 129745 + ... + 129833.

It is an arithmetic number, because the mean of its divisors is an integer number (324000).

Almost surely, 2^11551221 is an apocalyptic number.

11551221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11551221 is the 4806-th triangular number.

It is an amenable number.

11551221 is a deficient number, since it is larger than the sum of its proper divisors (9184779).

11551221 is a wasteful number, since it uses less digits than its factorization.

11551221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151 (or 145 counting only the distinct ones).

The product of its digits is 100, while the sum is 18.

The square root of 11551221 is about 3398.7087253838. The cubic root of 11551221 is about 226.0524912662.

Adding to 11551221 its reverse (12215511), we get a palindrome (23766732).

The spelling of 11551221 in words is "eleven million, five hundred fifty-one thousand, two hundred twenty-one".