81115081 has 2 divisors, whose sum is σ = 81115082. Its totient is φ = 81115080.

The previous prime is 81115079. The next prime is 81115087. The reversal of 81115081 is 18051118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56115081 + 25000000 = 7491^2 + 5000^2 .

It is a cyclic number.

It is not a de Polignac number, because 81115081 - 2¹ = 81115079 is a prime.

It is a super-2 number, since 2×81115081² = 13159312731273122, which contains 22 as substring.

Together with 81115079, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81115087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40557540 + 40557541.

It is an arithmetic number, because the mean of its divisors is an integer number (40557541).

Almost surely, 2^81115081 is an apocalyptic number.

It is an amenable number.

81115081 is a deficient number, since it is larger than the sum of its proper divisors (1).

81115081 is an equidigital number, since it uses as much as digits as its factorization.

81115081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 320, while the sum is 25.

The square root of 81115081 is about 9006.3911196439. The cubic root of 81115081 is about 432.8796821803.

Adding to 81115081 its reverse (18051118), we get a palindrome (99166199).

The spelling of 81115081 in words is "eighty-one million, one hundred fifteen thousand, eighty-one".