81891127 has 4 divisors (see below), whose sum is σ = 82307016. Its totient is φ = 81475240.

The previous prime is 81891079. The next prime is 81891137. The reversal of 81891127 is 72119818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 72119818 = 2 ⋅36059909.

It is a cyclic number.

It is not a de Polignac number, because 81891127 - 2¹¹ = 81889079 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81891137) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 207649 + ... + 208042.

It is an arithmetic number, because the mean of its divisors is an integer number (20576754).

Almost surely, 2^81891127 is an apocalyptic number.

81891127 is a deficient number, since it is larger than the sum of its proper divisors (415889).

81891127 is a wasteful number, since it uses less digits than its factorization.

81891127 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415888.

The product of its digits is 8064, while the sum is 37.

The square root of 81891127 is about 9049.3716356441. The cubic root of 81891127 is about 434.2557883236.

It can be divided in two parts, 8189 and 1127, that added together give a triangular number (9316 = T₁₃₆).

The spelling of 81891127 in words is "eighty-one million, eight hundred ninety-one thousand, one hundred twenty-seven".