81782172 has 36 divisors (see below), whose sum is σ = 218889216. Its totient is φ = 25656960.

The previous prime is 81782171. The next prime is 81782191. The reversal of 81782172 is 27128718.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81782171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 66204 + ... + 67427.

It is an arithmetic number, because the mean of its divisors is an integer number (6080256).

Almost surely, 2^81782172 is an apocalyptic number.

It is an amenable number.

81782172 is an abundant number, since it is smaller than the sum of its proper divisors (137107044).

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

81782172 is a wasteful number, since it uses less digits than its factorization.

81782172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133658 (or 133653 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 81782172 is about 9043.3496006734. The cubic root of 81782172 is about 434.0631124283.

The spelling of 81782172 in words is "eighty-one million, seven hundred eighty-two thousand, one hundred seventy-two".