81999903 has 4 divisors (see below), whose sum is σ = 109333208. Its totient is φ = 54666600.

The previous prime is 81999889. The next prime is 81999941. The reversal of 81999903 is 30999918.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81999903 - 2⁴ = 81999887 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 (81999503) 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, 13666648 + ... + 13666653.

It is an arithmetic number, because the mean of its divisors is an integer number (27333302).

Almost surely, 2^81999903 is an apocalyptic number.

81999903 is a deficient number, since it is larger than the sum of its proper divisors (27333305).

81999903 is a wasteful number, since it uses less digits than its factorization.

81999903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27333304.

The product of its (nonzero) digits is 157464, while the sum is 48.

The square root of 81999903 is about 9055.3797822068. The cubic root of 81999903 is about 434.4479772700.

The spelling of 81999903 in words is "eighty-one million, nine hundred ninety-nine thousand, nine hundred three".