81936361 has 4 divisors (see below), whose sum is σ = 88239172. Its totient is φ = 75633552.

The previous prime is 81936319. The next prime is 81936367. The reversal of 81936361 is 16363918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16363918 = 2 ⋅8181959.

It can be written as a sum of positive squares in 2 ways, for example, as 27825625 + 54110736 = 5275^2 + 7356^2 .

It is a cyclic number.

It is not a de Polignac number, because 81936361 - 2⁷ = 81936233 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81936361.

It is not an unprimeable number, because it can be changed into a prime (81936367) 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, 3151386 + ... + 3151411.

It is an arithmetic number, because the mean of its divisors is an integer number (22059793).

Almost surely, 2^81936361 is an apocalyptic number.

It is an amenable number.

81936361 is a deficient number, since it is larger than the sum of its proper divisors (6302811).

81936361 is a wasteful number, since it uses less digits than its factorization.

81936361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6302810.

The product of its digits is 23328, while the sum is 37.

The square root of 81936361 is about 9051.8705801619. The cubic root of 81936361 is about 434.3357298729.

The spelling of 81936361 in words is "eighty-one million, nine hundred thirty-six thousand, three hundred sixty-one".