8191821 has 12 divisors (see below), whose sum is σ = 12006176. Its totient is φ = 4964520.

The previous prime is 8191819. The next prime is 8191829. The reversal of 8191821 is 1281918.

It is not a de Polignac number, because 8191821 - 2¹ = 8191819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8191829) 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 11 ways as a sum of consecutive naturals, for example, 10921 + ... + 11646.

Almost surely, 2^8191821 is an apocalyptic number.

It is an amenable number.

8191821 is a deficient number, since it is larger than the sum of its proper divisors (3814355).

8191821 is a wasteful number, since it uses less digits than its factorization.

8191821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22592 (or 22581 counting only the distinct ones).

The product of its digits is 1152, while the sum is 30.

The square root of 8191821 is about 2862.1357410158. The cubic root of 8191821 is about 201.5858997051.

Subtracting from 8191821 its reverse (1281918), we obtain a triangular number (6909903 = T₃₇₁₇).

The spelling of 8191821 in words is "eight million, one hundred ninety-one thousand, eight hundred twenty-one".