81613678 has 4 divisors (see below), whose sum is σ = 122420520. Its totient is φ = 40806838.

The previous prime is 81613673. The next prime is 81613703. The reversal of 81613678 is 87631618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87631618 = 2 ⋅43815809.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 81613678.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81613673) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20403418 + ... + 20403421.

It is an arithmetic number, because the mean of its divisors is an integer number (30605130).

Almost surely, 2^81613678 is an apocalyptic number.

81613678 is a deficient number, since it is larger than the sum of its proper divisors (40806842).

81613678 is a wasteful number, since it uses less digits than its factorization.

81613678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40806841.

The product of its digits is 48384, while the sum is 40.

The square root of 81613678 is about 9034.0288908106. The cubic root of 81613678 is about 433.7648105964.

The spelling of 81613678 in words is "eighty-one million, six hundred thirteen thousand, six hundred seventy-eight".