81987971 has 8 divisors (see below), whose sum is σ = 90348720. Its totient is φ = 73920672.

The previous prime is 81987949. The next prime is 81987977. The reversal of 81987971 is 17978918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81987971 - 2²⁶ = 14879107 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81987977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 72776 + ... + 73893.

It is an arithmetic number, because the mean of its divisors is an integer number (11293590).

Almost surely, 2^81987971 is an apocalyptic number.

81987971 is a deficient number, since it is larger than the sum of its proper divisors (8360749).

81987971 is a wasteful number, since it uses less digits than its factorization.

81987971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146725.

The product of its digits is 254016, while the sum is 50.

The square root of 81987971 is about 9054.7209233637. The cubic root of 81987971 is about 434.4269037299.

The spelling of 81987971 in words is "eighty-one million, nine hundred eighty-seven thousand, nine hundred seventy-one".