8229721 has 4 divisors (see below), whose sum is σ = 8248500. Its totient is φ = 8210944.

The previous prime is 8229701. The next prime is 8229731. The reversal of 8229721 is 1279228.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4562496 + 3667225 = 2136^2 + 1915^2 .

It is a cyclic number.

It is not a de Polignac number, because 8229721 - 2¹¹ = 8227673 is a prime.

It is a Duffinian number.

8229721 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (8229701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8716 + ... + 9613.

It is an arithmetic number, because the mean of its divisors is an integer number (2062125).

Almost surely, 2^8229721 is an apocalyptic number.

It is an amenable number.

8229721 is a deficient number, since it is larger than the sum of its proper divisors (18779).

8229721 is a wasteful number, since it uses less digits than its factorization.

8229721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18778.

The product of its digits is 4032, while the sum is 31.

The square root of 8229721 is about 2868.7490305009. The cubic root of 8229721 is about 201.8963049783.

The spelling of 8229721 in words is "eight million, two hundred twenty-nine thousand, seven hundred twenty-one".