81994993 has 4 divisors (see below), whose sum is σ = 82016368. Its totient is φ = 81973620.

The previous prime is 81994967. The next prime is 81995003. The reversal of 81994993 is 39949918.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81994993 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 81994993.

It is not an unprimeable number, because it can be changed into a prime (81994933) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3171 + ... + 13192.

It is an arithmetic number, because the mean of its divisors is an integer number (20504092).

Almost surely, 2^81994993 is an apocalyptic number.

It is an amenable number.

81994993 is a deficient number, since it is larger than the sum of its proper divisors (21375).

81994993 is a wasteful number, since it uses less digits than its factorization.

81994993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21374.

The product of its digits is 629856, while the sum is 52.

The square root of 81994993 is about 9055.1086685914. The cubic root of 81994993 is about 434.4393057876.

The spelling of 81994993 in words is "eighty-one million, nine hundred ninety-four thousand, nine hundred ninety-three".