8687721 has 16 divisors (see below), whose sum is σ = 13814784. Its totient is φ = 4748304.

The previous prime is 8687713. The next prime is 8687729. The reversal of 8687721 is 1277868.

It is an interprime number because it is at equal distance from previous prime (8687713) and next prime (8687729).

It is not a de Polignac number, because 8687721 - 2³ = 8687713 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 8687721.

It is not an unprimeable number, because it can be changed into a prime (8687729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8511 + ... + 9476.

It is an arithmetic number, because the mean of its divisors is an integer number (863424).

Almost surely, 2^8687721 is an apocalyptic number.

It is an amenable number.

8687721 is a deficient number, since it is larger than the sum of its proper divisors (5127063).

8687721 is a wasteful number, since it uses less digits than its factorization.

8687721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18020.

The product of its digits is 37632, while the sum is 39.

The square root of 8687721 is about 2947.4940203502. The cubic root of 8687721 is about 205.5742061264.

The spelling of 8687721 in words is "eight million, six hundred eighty-seven thousand, seven hundred twenty-one".