81985699 has 4 divisors (see below), whose sum is σ = 82003864. Its totient is φ = 81967536.

The previous prime is 81985621. The next prime is 81985711. The reversal of 81985699 is 99658918.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 81985699 - 2⁹ = 81985187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81985619) 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, 3484 + ... + 13270.

It is an arithmetic number, because the mean of its divisors is an integer number (20500966).

Almost surely, 2^81985699 is an apocalyptic number.

81985699 is a deficient number, since it is larger than the sum of its proper divisors (18165).

81985699 is an equidigital number, since it uses as much as digits as its factorization.

81985699 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18164.

The product of its digits is 1399680, while the sum is 55.

The square root of 81985699 is about 9054.5954630784. The cubic root of 81985699 is about 434.4228908362.

The spelling of 81985699 in words is "eighty-one million, nine hundred eighty-five thousand, six hundred ninety-nine".