8728721 has 2 divisors, whose sum is σ = 8728722. Its totient is φ = 8728720.

The previous prime is 8728717. The next prime is 8728757. The reversal of 8728721 is 1278278.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8673025 + 55696 = 2945^2 + 236^2 .

It is a cyclic number.

It is not a de Polignac number, because 8728721 - 2² = 8728717 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (8728711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4364360 + 4364361.

It is an arithmetic number, because the mean of its divisors is an integer number (4364361).

Almost surely, 2^8728721 is an apocalyptic number.

It is an amenable number.

8728721 is a deficient number, since it is larger than the sum of its proper divisors (1).

8728721 is an equidigital number, since it uses as much as digits as its factorization.

8728721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12544, while the sum is 35.

The square root of 8728721 is about 2954.4408946533. The cubic root of 8728721 is about 205.8970878178.

It can be divided in two parts, 8728 and 721, that added together give a palindrome (9449).

The spelling of 8728721 in words is "eight million, seven hundred twenty-eight thousand, seven hundred twenty-one".