221118821 has 12 divisors (see below), whose sum is σ = 280604160. Its totient is φ = 172299960.

The previous prime is 221118797. The next prime is 221118829. The reversal of 221118821 is 128811122.

It is not a de Polignac number, because 221118821 - 2²⁶ = 154009957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221118829) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 204581 + ... + 205658.

It is an arithmetic number, because the mean of its divisors is an integer number (23383680).

Almost surely, 2^221118821 is an apocalyptic number.

It is an amenable number.

221118821 is a deficient number, since it is larger than the sum of its proper divisors (59485339).

221118821 is a wasteful number, since it uses less digits than its factorization.

221118821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410264 (or 410257 counting only the distinct ones).

The product of its digits is 512, while the sum is 26.

The square root of 221118821 is about 14870.0645930003. The cubic root of 221118821 is about 604.7026938932.

Adding to 221118821 its reverse (128811122), we get a palindrome (349929943).

The spelling of 221118821 in words is "two hundred twenty-one million, one hundred eighteen thousand, eight hundred twenty-one".