99999561 has 16 divisors (see below), whose sum is σ = 141042816. Its totient is φ = 62891136.

The previous prime is 99999551. The next prime is 99999563. The reversal of 99999561 is 16599999.

It is not a de Polignac number, because 99999561 - 2¹⁹ = 99475273 is a prime.

It is not an unprimeable number, because it can be changed into a prime (99999563) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4890 + ... + 14963.

It is an arithmetic number, because the mean of its divisors is an integer number (8815176).

Almost surely, 2^99999561 is an apocalyptic number.

It is an amenable number.

99999561 is a deficient number, since it is larger than the sum of its proper divisors (41043255).

99999561 is a wasteful number, since it uses less digits than its factorization.

99999561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19952.

The product of its digits is 1771470, while the sum is 57.

The square root of 99999561 is about 9999.9780499759. The cubic root of 99999561 is about 464.1582041411.

The spelling of 99999561 in words is "ninety-nine million, nine hundred ninety-nine thousand, five hundred sixty-one".