821224221 has 16 divisors (see below), whose sum is σ = 1103943168. Its totient is φ = 543006000.

The previous prime is 821224199. The next prime is 821224259. The reversal of 821224221 is 122422128.

It is a de Polignac number, because none of the positive numbers 2^k-821224221 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 821224191 and 821224200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821224021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 438930 + ... + 440796.

It is an arithmetic number, because the mean of its divisors is an integer number (68996448).

Almost surely, 2^821224221 is an apocalyptic number.

It is an amenable number.

821224221 is a deficient number, since it is larger than the sum of its proper divisors (282718947).

821224221 is a wasteful number, since it uses less digits than its factorization.

821224221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2992.

The product of its digits is 1024, while the sum is 24.

The square root of 821224221 is about 28657.0099801078. The cubic root of 821224221 is about 936.4557269675.

Adding to 821224221 its reverse (122422128), we get a palindrome (943646349).

The spelling of 821224221 in words is "eight hundred twenty-one million, two hundred twenty-four thousand, two hundred twenty-one".