99981509 has 2 divisors, whose sum is σ = 99981510. Its totient is φ = 99981508.

The previous prime is 99981491. The next prime is 99981517. The reversal of 99981509 is 90518999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 93064609 + 6916900 = 9647^2 + 2630^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-99981509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99981599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49990754 + 49990755.

It is an arithmetic number, because the mean of its divisors is an integer number (49990755).

Almost surely, 2^99981509 is an apocalyptic number.

It is an amenable number.

99981509 is a deficient number, since it is larger than the sum of its proper divisors (1).

99981509 is an equidigital number, since it uses as much as digits as its factorization.

99981509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 262440, while the sum is 50.

The square root of 99981509 is about 9999.0754072564. The cubic root of 99981509 is about 464.1302723913.

The spelling of 99981509 in words is "ninety-nine million, nine hundred eighty-one thousand, five hundred nine".