818221 has 4 divisors (see below), whose sum is σ = 820512. Its totient is φ = 815932.

The previous prime is 818219. The next prime is 818231. The reversal of 818221 is 122818.

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, and also an emirpimes, since its reverse is a distinct semiprime: 122818 = 2 ⋅61409.

It is a cyclic number.

It is not a de Polignac number, because 818221 - 2¹ = 818219 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 818192 and 818201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (818231) 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 3 ways as a sum of consecutive naturals, for example, 481 + ... + 1366.

It is an arithmetic number, because the mean of its divisors is an integer number (205128).

2⁸¹⁸²²¹ is an apocalyptic number.

It is an amenable number.

818221 is a deficient number, since it is larger than the sum of its proper divisors (2291).

818221 is a wasteful number, since it uses less digits than its factorization.

818221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2290.

The product of its digits is 256, while the sum is 22.

The square root of 818221 is about 904.5556920389. Note that the first 3 decimals coincide. The cubic root of 818221 is about 93.5312791532.

The spelling of 818221 in words is "eight hundred eighteen thousand, two hundred twenty-one".