221216221 has 4 divisors (see below), whose sum is σ = 232859200. Its totient is φ = 209573244.

The previous prime is 221216179. The next prime is 221216227. The reversal of 221216221 is 122612122.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 221216221 - 2²³ = 212827613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19), and also a Moran number because the ratio is a prime number: 11642959 = 221216221 / (2 + 2 + 1 + 2 + 1 + 6 + 2 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221216227) 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, 5821461 + ... + 5821498.

It is an arithmetic number, because the mean of its divisors is an integer number (58214800).

Almost surely, 2^221216221 is an apocalyptic number.

It is an amenable number.

221216221 is a deficient number, since it is larger than the sum of its proper divisors (11642979).

221216221 is a wasteful number, since it uses less digits than its factorization.

221216221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11642978.

The product of its digits is 192, while the sum is 19.

The square root of 221216221 is about 14873.3392686377. The cubic root of 221216221 is about 604.7914687825.

Adding to 221216221 its reverse (122612122), we get a palindrome (343828343).

The spelling of 221216221 in words is "two hundred twenty-one million, two hundred sixteen thousand, two hundred twenty-one".