8720639 has 4 divisors (see below), whose sum is σ = 9179640. Its totient is φ = 8261640.

The previous prime is 8720629. The next prime is 8720671. The reversal of 8720639 is 9360278.

8720639 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 8720639 - 2⁴ = 8720623 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 8720599 and 8720608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8720629) 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, 229472 + ... + 229509.

It is an arithmetic number, because the mean of its divisors is an integer number (2294910).

Almost surely, 2^8720639 is an apocalyptic number.

8720639 is a deficient number, since it is larger than the sum of its proper divisors (459001).

8720639 is a wasteful number, since it uses less digits than its factorization.

8720639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 459000.

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 8720639 is about 2953.0728064171. The cubic root of 8720639 is about 205.8335208829.

The spelling of 8720639 in words is "eight million, seven hundred twenty thousand, six hundred thirty-nine".