8720921 has 8 divisors (see below), whose sum is σ = 9656544. Its totient is φ = 7809120.

The previous prime is 8720911. The next prime is 8720941. The reversal of 8720921 is 1290278.

It is a happy number.

8720921 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 a de Polignac number, because none of the positive numbers 2^k-8720921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8720911) 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, 5180 + ... + 6653.

It is an arithmetic number, because the mean of its divisors is an integer number (1207068).

Almost surely, 2^8720921 is an apocalyptic number.

It is an amenable number.

8720921 is a deficient number, since it is larger than the sum of its proper divisors (935623).

8720921 is a wasteful number, since it uses less digits than its factorization.

8720921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11911.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 8720921 is about 2953.1205529067. The cubic root of 8720921 is about 205.8357395440.

The spelling of 8720921 in words is "eight million, seven hundred twenty thousand, nine hundred twenty-one".