221221643 has 4 divisors (see below), whose sum is σ = 223887048. Its totient is φ = 218556240.

The previous prime is 221221633. The next prime is 221221667. The reversal of 221221643 is 346122122.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 346122122 = 2 ⋅173061061.

It is a cyclic number.

It is not a de Polignac number, because 221221643 - 2¹² = 221217547 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221221603) 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, 1332578 + ... + 1332743.

It is an arithmetic number, because the mean of its divisors is an integer number (55971762).

Almost surely, 2^221221643 is an apocalyptic number.

221221643 is a deficient number, since it is larger than the sum of its proper divisors (2665405).

221221643 is an equidigital number, since it uses as much as digits as its factorization.

221221643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2665404.

The product of its digits is 1152, while the sum is 23.

The square root of 221221643 is about 14873.5215399716. The cubic root of 221221643 is about 604.7964098797.

Adding to 221221643 its reverse (346122122), we get a palindrome (567343765).

The spelling of 221221643 in words is "two hundred twenty-one million, two hundred twenty-one thousand, six hundred forty-three".