8709378721 has 4 divisors (see below), whose sum is σ = 8709594244. Its totient is φ = 8709163200.

The previous prime is 8709378719. The next prime is 8709378781. The reversal of 8709378721 is 1278739078.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3911877025 + 4797501696 = 62545^2 + 69264^2 .

It is a 3-Lehmer number, since φ(8709378721) divides (8709378721-1)³.

It is a cyclic number.

It is not a de Polignac number, because 8709378721 - 2¹ = 8709378719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8709378781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26940 + ... + 134701.

It is an arithmetic number, because the mean of its divisors is an integer number (2177398561).

Almost surely, 2^8709378721 is an apocalyptic number.

8709378721 is the 53881-st octagonal number.

It is an amenable number.

8709378721 is a deficient number, since it is larger than the sum of its proper divisors (215523).

8709378721 is a wasteful number, since it uses less digits than its factorization.

8709378721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215522.

The product of its (nonzero) digits is 1185408, while the sum is 52.

The square root of 8709378721 is about 93324.0522105636. The cubic root of 8709378721 is about 2057.4489048314.

The spelling of 8709378721 in words is "eight billion, seven hundred nine million, three hundred seventy-eight thousand, seven hundred twenty-one".