99809981 has 2 divisors, whose sum is σ = 99809982. Its totient is φ = 99809980.

The previous prime is 99809939. The next prime is 99810001. The reversal of 99809981 is 18990899.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 92813956 + 6996025 = 9634^2 + 2645^2 .

It is a cyclic number.

It is not a de Polignac number, because 99809981 - 2²⁶ = 32701117 is a prime.

It is a super-2 number, since 2×99809981² = 19924064614440722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99809911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49904990 + 49904991.

It is an arithmetic number, because the mean of its divisors is an integer number (49904991).

Almost surely, 2^99809981 is an apocalyptic number.

It is an amenable number.

99809981 is a deficient number, since it is larger than the sum of its proper divisors (1).

99809981 is an equidigital number, since it uses as much as digits as its factorization.

99809981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 419904, while the sum is 53.

The square root of 99809981 is about 9990.4945323042. The cubic root of 99809981 is about 463.8647002584.

The spelling of 99809981 in words is "ninety-nine million, eight hundred nine thousand, nine hundred eighty-one".