81706891 has 16 divisors (see below), whose sum is σ = 98965440. Its totient is φ = 65963520.

The previous prime is 81706861. The next prime is 81706901. The reversal of 81706891 is 19860718.

It is not a de Polignac number, because 81706891 - 2⁷ = 81706763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81706831) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3415 + ... + 13231.

It is an arithmetic number, because the mean of its divisors is an integer number (6185340).

Almost surely, 2^81706891 is an apocalyptic number.

81706891 is a deficient number, since it is larger than the sum of its proper divisors (17258549).

81706891 is a wasteful number, since it uses less digits than its factorization.

81706891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9894.

The product of its (nonzero) digits is 24192, while the sum is 40.

The square root of 81706891 is about 9039.1864125042. The cubic root of 81706891 is about 433.9298856061.

The spelling of 81706891 in words is "eighty-one million, seven hundred six thousand, eight hundred ninety-one".