8305721 has 4 divisors (see below), whose sum is σ = 8419572. Its totient is φ = 8191872.

The previous prime is 8305711. The next prime is 8305729. The reversal of 8305721 is 1275038.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1275038 = 2 ⋅637519.

It can be written as a sum of positive squares in 2 ways, for example, as 1488400 + 6817321 = 1220^2 + 2611^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8305721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8305729) 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, 56816 + ... + 56961.

It is an arithmetic number, because the mean of its divisors is an integer number (2104893).

Almost surely, 2^8305721 is an apocalyptic number.

It is an amenable number.

8305721 is a deficient number, since it is larger than the sum of its proper divisors (113851).

8305721 is a wasteful number, since it uses less digits than its factorization.

8305721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113850.

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 8305721 is about 2881.9647811866. The cubic root of 8305721 is about 202.5158936872.

The spelling of 8305721 in words is "eight million, three hundred five thousand, seven hundred twenty-one".