81411581 has 4 divisors (see below), whose sum is σ = 83611932. Its totient is φ = 79211232.

The previous prime is 81411569. The next prime is 81411619. The reversal of 81411581 is 18511418.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 78605956 + 2805625 = 8866^2 + 1675^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81411581 is a prime.

It is a super-2 number, since 2×81411581² = 13255691041839122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81411481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1100120 + ... + 1100193.

It is an arithmetic number, because the mean of its divisors is an integer number (20902983).

Almost surely, 2^81411581 is an apocalyptic number.

It is an amenable number.

81411581 is a deficient number, since it is larger than the sum of its proper divisors (2200351).

81411581 is a wasteful number, since it uses less digits than its factorization.

81411581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2200350.

The product of its digits is 1280, while the sum is 29.

The square root of 81411581 is about 9022.8366382197. The cubic root of 81411581 is about 433.4064759507.

Adding to 81411581 its reverse (18511418), we get a palindrome (99922999).

The spelling of 81411581 in words is "eighty-one million, four hundred eleven thousand, five hundred eighty-one".