8563721 has 4 divisors (see below), whose sum is σ = 8573712. Its totient is φ = 8553732.

The previous prime is 8563717. The next prime is 8563727. The reversal of 8563721 is 1273658.

It is a happy number.

8563721 is digitally balanced in base 3, 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, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1273658 = 2 ⋅636829.

It is a cyclic number.

It is not a de Polignac number, because 8563721 - 2² = 8563717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8563727) 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, 3575 + ... + 5468.

It is an arithmetic number, because the mean of its divisors is an integer number (2143428).

Almost surely, 2^8563721 is an apocalyptic number.

It is an amenable number.

8563721 is a deficient number, since it is larger than the sum of its proper divisors (9991).

8563721 is an equidigital number, since it uses as much as digits as its factorization.

8563721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9990.

The product of its digits is 10080, while the sum is 32.

The square root of 8563721 is about 2926.3836043827. The cubic root of 8563721 is about 204.5914608135.

It can be divided in two parts, 85637 and 21, that added together give a palindrome (85658).

The spelling of 8563721 in words is "eight million, five hundred sixty-three thousand, seven hundred twenty-one".