81929787 has 4 divisors (see below), whose sum is σ = 109239720. Its totient is φ = 54619856.

The previous prime is 81929777. The next prime is 81929821. The reversal of 81929787 is 78792918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81929787 - 2¹¹ = 81927739 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81929707) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13654962 + ... + 13654967.

It is an arithmetic number, because the mean of its divisors is an integer number (27309930).

Almost surely, 2^81929787 is an apocalyptic number.

81929787 is a deficient number, since it is larger than the sum of its proper divisors (27309933).

81929787 is a wasteful number, since it uses less digits than its factorization.

81929787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27309932.

The product of its digits is 508032, while the sum is 51.

The square root of 81929787 is about 9051.5074435146. The cubic root of 81929787 is about 434.3241135428.

The spelling of 81929787 in words is "eighty-one million, nine hundred twenty-nine thousand, seven hundred eighty-seven".