81947 has 6 divisors (see below), whose sum is σ = 86868. Its totient is φ = 77292.

The previous prime is 81943. The next prime is 81953. The reversal of 81947 is 74918.

It is not a de Polignac number, because 81947 - 2² = 81943 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81943) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 248 + ... + 474.

It is an arithmetic number, because the mean of its divisors is an integer number (14478).

2⁸¹⁹⁴⁷ is an apocalyptic number.

81947 is a deficient number, since it is larger than the sum of its proper divisors (4921).

81947 is a wasteful number, since it uses less digits than its factorization.

81947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265 (or 246 counting only the distinct ones).

The product of its digits is 2016, while the sum is 29.

The square root of 81947 is about 286.2638642931. The cubic root of 81947 is about 43.4354527786.

Subtracting from 81947 its sum of digits (29), we obtain a palindrome (81918).

It can be divided in two parts, 8 and 1947, that multiplied together give a triangular number (15576 = T₁₇₆).

The spelling of 81947 in words is "eighty-one thousand, nine hundred forty-seven".