81505878 has 8 divisors (see below), whose sum is σ = 163011768. Its totient is φ = 27168624.

The previous prime is 81505867. The next prime is 81505901. The reversal of 81505878 is 87850518.

It is a sphenic number, since it is the product of 3 distinct primes.

81505878 is an admirable number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6792151 + ... + 6792162.

It is an arithmetic number, because the mean of its divisors is an integer number (20376471).

Almost surely, 2^81505878 is an apocalyptic number.

81505878 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81505878 is a wasteful number, since it uses less digits than its factorization.

81505878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13584318.

The product of its (nonzero) digits is 89600, while the sum is 42.

The square root of 81505878 is about 9028.0605890745. The cubic root of 81505878 is about 433.5737460162.

It can be divided in two parts, 8150 and 5878, that added together give a triangular number (14028 = T₁₆₇).

The spelling of 81505878 in words is "eighty-one million, five hundred five thousand, eight hundred seventy-eight".