81418691 has 4 divisors (see below), whose sum is σ = 81440472. Its totient is φ = 81396912.

The previous prime is 81418681. The next prime is 81418693. The reversal of 81418691 is 19681418.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19681418 = 2 ⋅9840709.

It is a cyclic number.

It is not a de Polignac number, because 81418691 - 2¹⁰ = 81417667 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81418693) 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, 3701 + ... + 13286.

It is an arithmetic number, because the mean of its divisors is an integer number (20360118).

Almost surely, 2^81418691 is an apocalyptic number.

81418691 is a deficient number, since it is larger than the sum of its proper divisors (21781).

81418691 is a wasteful number, since it uses less digits than its factorization.

81418691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21780.

The product of its digits is 13824, while the sum is 38.

The square root of 81418691 is about 9023.2306298797. The cubic root of 81418691 is about 433.4190926255.

The spelling of 81418691 in words is "eighty-one million, four hundred eighteen thousand, six hundred ninety-one".