81311899 has 8 divisors (see below), whose sum is σ = 82345088. Its totient is φ = 80282880.

The previous prime is 81311873. The next prime is 81311917. The reversal of 81311899 is 99811318.

It is a happy number.

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 81311899 - 2¹⁹ = 80787611 is a prime.

It is a super-2 number, since 2×81311899² = 13223249837972402, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81311809) 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, 58189 + ... + 59569.

It is an arithmetic number, because the mean of its divisors is an integer number (10293136).

Almost surely, 2^81311899 is an apocalyptic number.

81311899 is a deficient number, since it is larger than the sum of its proper divisors (1033189).

81311899 is a wasteful number, since it uses less digits than its factorization.

81311899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2085.

The product of its digits is 15552, while the sum is 40.

The square root of 81311899 is about 9017.3110737071. The cubic root of 81311899 is about 433.2295131295.

The spelling of 81311899 in words is "eighty-one million, three hundred eleven thousand, eight hundred ninety-nine".