81987816 has 32 divisors (see below), whose sum is σ = 208447200. Its totient is φ = 26865600.

The previous prime is 81987811. The next prime is 81987817. The reversal of 81987816 is 61878918.

It is not an unprimeable number, because it can be changed into a prime (81987811) 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, 27535 + ... + 30366.

It is an arithmetic number, because the mean of its divisors is an integer number (6513975).

Almost surely, 2^81987816 is an apocalyptic number.

It is an amenable number.

81987816 is an abundant number, since it is smaller than the sum of its proper divisors (126459384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81987816 is a wasteful number, since it uses less digits than its factorization.

81987816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57969 (or 57965 counting only the distinct ones).

The product of its digits is 193536, while the sum is 48.

The square root of 81987816 is about 9054.7123642886. The cubic root of 81987816 is about 434.4266299653.

The spelling of 81987816 in words is "eighty-one million, nine hundred eighty-seven thousand, eight hundred sixteen".