221216641 has 4 divisors (see below), whose sum is σ = 221249284. Its totient is φ = 221184000.

The previous prime is 221216629. The next prime is 221216659. The reversal of 221216641 is 146612122.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 106812225 + 114404416 = 10335^2 + 10696^2 .

It is a 3-Lehmer number, since φ(221216641) divides (221216641-1)³.

It is a cyclic number.

It is not a de Polignac number, because 221216641 - 2⁹ = 221216129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221216041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1920 + ... + 21121.

It is an arithmetic number, because the mean of its divisors is an integer number (55312321).

Almost surely, 2^221216641 is an apocalyptic number.

It is an amenable number.

221216641 is a deficient number, since it is larger than the sum of its proper divisors (32643).

221216641 is an equidigital number, since it uses as much as digits as its factorization.

221216641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32642.

The product of its digits is 1152, while the sum is 25.

The square root of 221216641 is about 14873.3533878544. The cubic root of 221216641 is about 604.7918515336.

Adding to 221216641 its reverse (146612122), we get a palindrome (367828763).

The spelling of 221216641 in words is "two hundred twenty-one million, two hundred sixteen thousand, six hundred forty-one".