8381721 has 8 divisors (see below), whose sum is σ = 11477824. Its totient is φ = 5436720.

The previous prime is 8381719. The next prime is 8381777. The reversal of 8381721 is 1271838.

It is a happy number.

8381721 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 8381721 - 2¹ = 8381719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8380721) 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, 37645 + ... + 37866.

It is an arithmetic number, because the mean of its divisors is an integer number (1434728).

Almost surely, 2^8381721 is an apocalyptic number.

It is an amenable number.

8381721 is a deficient number, since it is larger than the sum of its proper divisors (3096103).

8381721 is a wasteful number, since it uses less digits than its factorization.

8381721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75551.

The product of its digits is 2688, while the sum is 30.

The square root of 8381721 is about 2895.1202047583. The cubic root of 8381721 is about 203.1317142080.

It can be divided in two parts, 83817 and 21, that added together give a palindrome (83838).

The spelling of 8381721 in words is "eight million, three hundred eighty-one thousand, seven hundred twenty-one".