8021721 has 8 divisors (see below), whose sum is σ = 10720864. Its totient is φ = 5335200.

The previous prime is 8021681. The next prime is 8021729. The reversal of 8021721 is 1271208.

8021721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 8021721 - 2⁷ = 8021593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8021729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1555 + ... + 4296.

It is an arithmetic number, because the mean of its divisors is an integer number (1340108).

Almost surely, 2^8021721 is an apocalyptic number.

It is an amenable number.

8021721 is a deficient number, since it is larger than the sum of its proper divisors (2699143).

8021721 is a wasteful number, since it uses less digits than its factorization.

8021721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6311.

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 8021721 is about 2832.2642885155. The cubic root of 8021721 is about 200.1808447599.

Adding to 8021721 its reverse (1271208), we get a palindrome (9292929).

The spelling of 8021721 in words is "eight million, twenty-one thousand, seven hundred twenty-one".