81987028 has 6 divisors (see below), whose sum is σ = 143477306. Its totient is φ = 40993512.

The previous prime is 81987011. The next prime is 81987041. The reversal of 81987028 is 82078918.

It can be written as a sum of positive squares in only one way, i.e., 81216144 + 770884 = 9012^2 + 878^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10248375 + ... + 10248382.

Almost surely, 2^81987028 is an apocalyptic number.

It is an amenable number.

81987028 is a deficient number, since it is larger than the sum of its proper divisors (61490278).

81987028 is a wasteful number, since it uses less digits than its factorization.

81987028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20496761 (or 20496759 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 43.

The square root of 81987028 is about 9054.6688509299. The cubic root of 81987028 is about 434.4252381761.

The spelling of 81987028 in words is "eighty-one million, nine hundred eighty-seven thousand, twenty-eight".