81785655 has 72 divisors (see below), whose sum is σ = 170726400. Its totient is φ = 36070272.

The previous prime is 81785621. The next prime is 81785701. The reversal of 81785655 is 55658718.

81785655 is a `hidden beast` number, since 81 + 7 + 8 + 565 + 5 = 666.

81785655 is a nontrivial binomial coefficient, being equal to C(12790, 2).

It is not a de Polignac number, because 81785655 - 2⁶ = 81785591 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81785655.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 63306 + ... + 64584.

It is an arithmetic number, because the mean of its divisors is an integer number (2371200).

Almost surely, 2^81785655 is an apocalyptic number.

81785655 is the 12789-th triangular number and also the 6395-th hexagonal number.

81785655 is an abundant number, since it is smaller than the sum of its proper divisors (88940745).

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

81785655 is a wasteful number, since it uses less digits than its factorization.

81785655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1333 (or 1323 counting only the distinct ones).

The product of its digits is 336000, while the sum is 45.

The square root of 81785655 is about 9043.5421710743. The cubic root of 81785655 is about 434.0692744085.

The spelling of 81785655 in words is "eighty-one million, seven hundred eighty-five thousand, six hundred fifty-five".