9867591721 has 8 divisors (see below), whose sum is σ = 11088665280. Its totient is φ = 8712522192.

The previous prime is 9867591667. The next prime is 9867591733. The reversal of 9867591721 is 1271957689.

It is a happy number.

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 9867591721 - 2⁷ = 9867591593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9867591751) 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, 16500691 + ... + 16501288.

It is an arithmetic number, because the mean of its divisors is an integer number (1386083160).

Almost surely, 2^9867591721 is an apocalyptic number.

It is an amenable number.

9867591721 is a deficient number, since it is larger than the sum of its proper divisors (1221073559).

9867591721 is a wasteful number, since it uses less digits than its factorization.

9867591721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33002015.

The product of its digits is 1905120, while the sum is 55.

The square root of 9867591721 is about 99335.7524811686. The cubic root of 9867591721 is about 2144.8835773029.

The spelling of 9867591721 in words is "nine billion, eight hundred sixty-seven million, five hundred ninety-one thousand, seven hundred twenty-one".