9891218705 has 4 divisors (see below), whose sum is σ = 11869462452. Its totient is φ = 7912974960.

The previous prime is 9891218693. The next prime is 9891218707. The reversal of 9891218705 is 5078121989.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5078121989 = 461 ⋅11015449.

It can be written as a sum of positive squares in 2 ways, for example, as 6883025296 + 3008193409 = 82964^2 + 54847^2 .

It is not a de Polignac number, because 9891218705 - 2¹⁰ = 9891217681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9891218707) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 989121866 + ... + 989121875.

It is an arithmetic number, because the mean of its divisors is an integer number (2967365613).

Almost surely, 2^9891218705 is an apocalyptic number.

It is an amenable number.

9891218705 is a deficient number, since it is larger than the sum of its proper divisors (1978243747).

9891218705 is a wasteful number, since it uses less digits than its factorization.

9891218705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1978243746.

The product of its (nonzero) digits is 362880, while the sum is 50.

The square root of 9891218705 is about 99454.6062533053. The cubic root of 9891218705 is about 2146.5941174890.

The spelling of 9891218705 in words is "nine billion, eight hundred ninety-one million, two hundred eighteen thousand, seven hundred five".