813121221 has 16 divisors (see below), whose sum is σ = 1194919488. Its totient is φ = 487718400.

The previous prime is 813121201. The next prime is 813121223. The reversal of 813121221 is 122121318.

It is not a de Polignac number, because 813121221 - 2⁹ = 813120709 is a prime.

It is a super-2 number, since 2×813121221² = 1322332240081061682, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (813121223) 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 15 ways as a sum of consecutive naturals, for example, 123810 + ... + 130211.

It is an arithmetic number, because the mean of its divisors is an integer number (74682468).

Almost surely, 2^813121221 is an apocalyptic number.

It is an amenable number.

813121221 is a deficient number, since it is larger than the sum of its proper divisors (381798267).

813121221 is a wasteful number, since it uses less digits than its factorization.

813121221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254132.

The product of its digits is 192, while the sum is 21.

The square root of 813121221 is about 28515.2804825764. The cubic root of 813121221 is about 933.3655454727.

Adding to 813121221 its reverse (122121318), we get a palindrome (935242539).

The spelling of 813121221 in words is "eight hundred thirteen million, one hundred twenty-one thousand, two hundred twenty-one".