8219991 has 24 divisors (see below), whose sum is σ = 12274176. Its totient is φ = 4885920.

The previous prime is 8219983. The next prime is 8220013. The reversal of 8219991 is 1999128.

It is a happy number.

It is not a de Polignac number, because 8219991 - 2³ = 8219983 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8219941) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15456 + ... + 15978.

It is an arithmetic number, because the mean of its divisors is an integer number (511424).

Almost surely, 2^8219991 is an apocalyptic number.

8219991 is a deficient number, since it is larger than the sum of its proper divisors (4054185).

8219991 is a wasteful number, since it uses less digits than its factorization.

8219991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 583 (or 570 counting only the distinct ones).

The product of its digits is 11664, while the sum is 39.

The square root of 8219991 is about 2867.0526678106. The cubic root of 8219991 is about 201.8167062594.

The spelling of 8219991 in words is "eight million, two hundred nineteen thousand, nine hundred ninety-one".