81825178 has 4 divisors (see below), whose sum is σ = 122737770. Its totient is φ = 40912588.

The previous prime is 81825169. The next prime is 81825179. The reversal of 81825178 is 87152818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87152818 = 2 ⋅43576409.

It can be written as a sum of positive squares in only one way, i.e., 69272329 + 12552849 = 8323^2 + 3543^2 .

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 81825178.

It is not an unprimeable number, because it can be changed into a prime (81825179) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20456293 + ... + 20456296.

Almost surely, 2^81825178 is an apocalyptic number.

81825178 is a deficient number, since it is larger than the sum of its proper divisors (40912592).

81825178 is a wasteful number, since it uses less digits than its factorization.

81825178 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40912591.

The product of its digits is 35840, while the sum is 40.

The square root of 81825178 is about 9045.7270575670. The cubic root of 81825178 is about 434.1391846194.

The spelling of 81825178 in words is "eighty-one million, eight hundred twenty-five thousand, one hundred seventy-eight".