81993012 has 24 divisors (see below), whose sum is σ = 193214112. Its totient is φ = 27060000.

The previous prime is 81993011. The next prime is 81993017. The reversal of 81993012 is 21039918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81993011) 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 7 ways as a sum of consecutive naturals, for example, 32614 + ... + 35037.

It is an arithmetic number, because the mean of its divisors is an integer number (8050588).

Almost surely, 2^81993012 is an apocalyptic number.

It is an amenable number.

81993012 is an abundant number, since it is smaller than the sum of its proper divisors (111221100).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81993012 is a wasteful number, since it uses less digits than its factorization.

81993012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67759 (or 67757 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 81993012 is about 9054.9992821645. Note that the first 3 decimals coincide. The cubic root of 81993012 is about 434.4358070732.

It can be divided in two parts, 8199 and 3012, that added together give a palindrome (11211).

The spelling of 81993012 in words is "eighty-one million, nine hundred ninety-three thousand, twelve".