99999916561 has 4 divisors (see below), whose sum is σ = 105882264612. Its totient is φ = 94117568512.

The previous prime is 99999916531. The next prime is 99999916571. The reversal of 99999916561 is 16561999999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16561999999 = 13177 ⋅1256887.

It can be written as a sum of positive squares in 2 ways, for example, as 83503082961 + 16496833600 = 288969^2 + 128440^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-99999916561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (99999916531) 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, 2941174000 + ... + 2941174033.

It is an arithmetic number, because the mean of its divisors is an integer number (26470566153).

Almost surely, 2^99999916561 is an apocalyptic number.

It is an amenable number.

99999916561 is a deficient number, since it is larger than the sum of its proper divisors (5882348051).

99999916561 is a wasteful number, since it uses less digits than its factorization.

99999916561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5882348050.

The product of its digits is 95659380, while the sum is 73.

The spelling of 99999916561 in words is "ninety-nine billion, nine hundred ninety-nine million, nine hundred sixteen thousand, five hundred sixty-one".