8720821 has 8 divisors (see below), whose sum is σ = 8877600. Its totient is φ = 8565648.

The previous prime is 8720819. The next prime is 8720837. The reversal of 8720821 is 1280278.

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

It is a cyclic number.

It is not a de Polignac number, because 8720821 - 2¹ = 8720819 is a prime.

It is a Duffinian number.

8720821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 8720821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8720891) 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, 15670 + ... + 16216.

It is an arithmetic number, because the mean of its divisors is an integer number (1109700).

Almost surely, 2^8720821 is an apocalyptic number.

It is an amenable number.

8720821 is a deficient number, since it is larger than the sum of its proper divisors (156779).

8720821 is a wasteful number, since it uses less digits than its factorization.

8720821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 803.

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 8720821 is about 2953.1036216157. The cubic root of 8720821 is about 205.8349527902.

The spelling of 8720821 in words is "eight million, seven hundred twenty thousand, eight hundred twenty-one".