81993709 has 12 divisors (see below), whose sum is σ = 97412544. Its totient is φ = 68783064.

The previous prime is 81993677. The next prime is 81993713. The reversal of 81993709 is 90739918.

It is not a de Polignac number, because 81993709 - 2⁵ = 81993677 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81993209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15499 + ... + 20104.

It is an arithmetic number, because the mean of its divisors is an integer number (8117712).

Almost surely, 2^81993709 is an apocalyptic number.

It is an amenable number.

81993709 is a deficient number, since it is larger than the sum of its proper divisors (15418835).

81993709 is a wasteful number, since it uses less digits than its factorization.

81993709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35664 (or 35657 counting only the distinct ones).

The product of its (nonzero) digits is 122472, while the sum is 46.

The square root of 81993709 is about 9055.0377691095. The cubic root of 81993709 is about 434.4370380760.

The spelling of 81993709 in words is "eighty-one million, nine hundred ninety-three thousand, seven hundred nine".