81981899 has 8 divisors (see below), whose sum is σ = 84478560. Its totient is φ = 79500096.

The previous prime is 81981883. The next prime is 81981901. The reversal of 81981899 is 99818918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81981899 - 2⁴ = 81981883 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 81981899.

It is not an unprimeable number, because it can be changed into a prime (81981829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8042 + ... + 15120.

It is an arithmetic number, because the mean of its divisors is an integer number (10559820).

Almost surely, 2^81981899 is an apocalyptic number.

81981899 is a deficient number, since it is larger than the sum of its proper divisors (2496661).

81981899 is a wasteful number, since it uses less digits than its factorization.

81981899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7429.

The product of its digits is 373248, while the sum is 53.

The square root of 81981899 is about 9054.3856224484. The cubic root of 81981899 is about 434.4161789645.

The spelling of 81981899 in words is "eighty-one million, nine hundred eighty-one thousand, eight hundred ninety-nine".