81500081 has 12 divisors (see below), whose sum is σ = 89096112. Its totient is φ = 74511216.

The previous prime is 81500077. The next prime is 81500117. The reversal of 81500081 is 18000518.

It is not a de Polignac number, because 81500081 - 2² = 81500077 is a prime.

It is a super-2 number, since 2×81500081² = 13284526406013122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81500681) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15830 + ... + 20336.

It is an arithmetic number, because the mean of its divisors is an integer number (7424676).

Almost surely, 2^81500081 is an apocalyptic number.

It is an amenable number.

81500081 is a deficient number, since it is larger than the sum of its proper divisors (7596031).

81500081 is a wasteful number, since it uses less digits than its factorization.

81500081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4640 (or 4627 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 23.

The square root of 81500081 is about 9027.7395288079. The cubic root of 81500081 is about 433.5634666488.

Adding to 81500081 its reverse (18000518), we get a palindrome (99500599).

The spelling of 81500081 in words is "eighty-one million, five hundred thousand, eighty-one".