99981605 has 4 divisors (see below), whose sum is σ = 119977932. Its totient is φ = 79985280.

The previous prime is 99981601. The next prime is 99981613. The reversal of 99981605 is 50618999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50618999 = 433 ⋅116903.

It can be written as a sum of positive squares in 2 ways, for example, as 69522244 + 30459361 = 8338^2 + 5519^2 .

It is not a de Polignac number, because 99981605 - 2² = 99981601 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 99981605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99981601) 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, 9998156 + ... + 9998165.

It is an arithmetic number, because the mean of its divisors is an integer number (29994483).

Almost surely, 2^99981605 is an apocalyptic number.

It is an amenable number.

99981605 is a deficient number, since it is larger than the sum of its proper divisors (19996327).

99981605 is a wasteful number, since it uses less digits than its factorization.

99981605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19996326.

The product of its (nonzero) digits is 174960, while the sum is 47.

The square root of 99981605 is about 9999.0802076991. The cubic root of 99981605 is about 464.1304209405.

The spelling of 99981605 in words is "ninety-nine million, nine hundred eighty-one thousand, six hundred five".