81505081 has 24 divisors (see below), whose sum is σ = 98233344. Its totient is φ = 67384800.

The previous prime is 81505069. The next prime is 81505091. The reversal of 81505081 is 18050518.

It is not a de Polignac number, because 81505081 - 2¹⁷ = 81374009 is a prime.

It is a super-3 number, since 3×81505081³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81505091) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 212616 + ... + 212998.

It is an arithmetic number, because the mean of its divisors is an integer number (4093056).

Almost surely, 2^81505081 is an apocalyptic number.

It is an amenable number.

81505081 is a deficient number, since it is larger than the sum of its proper divisors (16728263).

81505081 is a wasteful number, since it uses less digits than its factorization.

81505081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 541 (or 534 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 28.

The square root of 81505081 is about 9028.0164488109. The cubic root of 81505081 is about 433.5723327872.

Adding to 81505081 its reverse (18050518), we get a palindrome (99555599).

It can be divided in two parts, 8150 and 5081, that added together give a palindrome (13231).

The spelling of 81505081 in words is "eighty-one million, five hundred five thousand, eighty-one".