8735561721 has 40 divisors (see below), whose sum is σ = 13385500128. Its totient is φ = 5674104000.

The previous prime is 8735561711. The next prime is 8735561761. The reversal of 8735561721 is 1271655378.

It is a happy number.

8735561721 is a `hidden beast` number, since 8 + 7 + 3 + 5 + 5 + 617 + 21 = 666.

8735561721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 8735561721 - 2⁹ = 8735561209 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (8735561701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 3622006 + ... + 3624416.

Almost surely, 2^8735561721 is an apocalyptic number.

8735561721 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

8735561721 is a deficient number, since it is larger than the sum of its proper divisors (4649938407).

8735561721 is a wasteful number, since it uses less digits than its factorization.

8735561721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3555 (or 3546 counting only the distinct ones).

The product of its digits is 352800, while the sum is 45.

The square root of 8735561721 is about 93464.2269587675. The cubic root of 8735561721 is about 2059.5086113110.

The spelling of 8735561721 in words is "eight billion, seven hundred thirty-five million, five hundred sixty-one thousand, seven hundred twenty-one".