8721605 has 8 divisors (see below), whose sum is σ = 10827000. Its totient is φ = 6736576.

The previous prime is 8721599. The next prime is 8721607. The reversal of 8721605 is 5061278.

8721605 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 432964 + 8288641 = 658^2 + 2879^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 8721605 - 2⁶ = 8721541 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8721607) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29930 + ... + 30219.

It is an arithmetic number, because the mean of its divisors is an integer number (1353375).

Almost surely, 2^8721605 is an apocalyptic number.

It is an amenable number.

8721605 is a deficient number, since it is larger than the sum of its proper divisors (2105395).

8721605 is a wasteful number, since it uses less digits than its factorization.

8721605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60183.

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 8721605 is about 2953.2363603342. The cubic root of 8721605 is about 205.8411207786.

Subtracting from 8721605 its sum of digits (29), we obtain a triangular number (8721576 = T₄₁₇₆).

The spelling of 8721605 in words is "eight million, seven hundred twenty-one thousand, six hundred five".