8721645 has 8 divisors (see below), whose sum is σ = 13954656. Its totient is φ = 4651536.

The previous prime is 8721631. The next prime is 8721667. The reversal of 8721645 is 5461278.

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

It is not a de Polignac number, because 8721645 - 2¹⁴ = 8705261 is a prime.

It is a super-3 number, since 3×8721645³ (a number of 22 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

8721645 is a lucky number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 290707 + ... + 290736.

It is an arithmetic number, because the mean of its divisors is an integer number (1744332).

Almost surely, 2^8721645 is an apocalyptic number.

It is an amenable number.

8721645 is a deficient number, since it is larger than the sum of its proper divisors (5233011).

8721645 is a wasteful number, since it uses less digits than its factorization.

8721645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 581451.

The product of its digits is 13440, while the sum is 33.

The square root of 8721645 is about 2953.2431325578. The cubic root of 8721645 is about 205.8414354620.

The spelling of 8721645 in words is "eight million, seven hundred twenty-one thousand, six hundred forty-five".