81371780 has 24 divisors (see below), whose sum is σ = 195292608. Its totient is φ = 27898848.

The previous prime is 81371779. The next prime is 81371791. The reversal of 81371780 is 8717318.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 81371780.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 290474 + ... + 290753.

It is an arithmetic number, because the mean of its divisors is an integer number (8137192).

Almost surely, 2^81371780 is an apocalyptic number.

It is an amenable number.

81371780 is an abundant number, since it is smaller than the sum of its proper divisors (113920828).

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

81371780 is a wasteful number, since it uses less digits than its factorization.

81371780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 581243 (or 581241 counting only the distinct ones).

The product of its (nonzero) digits is 9408, while the sum is 35.

The square root of 81371780 is about 9020.6307983422. The cubic root of 81371780 is about 433.3358356200.

The spelling of 81371780 in words is "eighty-one million, three hundred seventy-one thousand, seven hundred eighty".