8163721 has 4 divisors (see below), whose sum is σ = 8170132. Its totient is φ = 8157312.

The previous prime is 8163713. The next prime is 8163737. The reversal of 8163721 is 1273618.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1273618 = 2 ⋅636809.

It can be written as a sum of positive squares in 2 ways, for example, as 546121 + 7617600 = 739^2 + 2760^2 .

It is a cyclic number.

It is not a de Polignac number, because 8163721 - 2³ = 8163713 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 8163721.

It is not an unprimeable number, because it can be changed into a prime (8163121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 576 + ... + 4081.

It is an arithmetic number, because the mean of its divisors is an integer number (2042533).

Almost surely, 2^8163721 is an apocalyptic number.

It is an amenable number.

8163721 is a deficient number, since it is larger than the sum of its proper divisors (6411).

8163721 is a wasteful number, since it uses less digits than its factorization.

8163721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6410.

The product of its digits is 2016, while the sum is 28.

The square root of 8163721 is about 2857.2226024585. Note that the first 3 decimals coincide. The cubic root of 8163721 is about 201.3551389210.

The spelling of 8163721 in words is "eight million, one hundred sixty-three thousand, seven hundred twenty-one".