81747828 has 18 divisors (see below), whose sum is σ = 206640434. Its totient is φ = 27249264.

The previous prime is 81747821. The next prime is 81747829. The reversal of 81747828 is 82874718.

It can be written as a sum of positive squares in only one way, i.e., 47032164 + 34715664 = 6858^2 + 5892^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81747821) 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, 1135351 + ... + 1135422.

Almost surely, 2^81747828 is an apocalyptic number.

It is an amenable number.

81747828 is an abundant number, since it is smaller than the sum of its proper divisors (124892606).

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

81747828 is a wasteful number, since it uses less digits than its factorization.

81747828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2270783 (or 2270778 counting only the distinct ones).

The product of its digits is 200704, while the sum is 45.

The square root of 81747828 is about 9041.4505473403. The cubic root of 81747828 is about 434.0023430682.

The spelling of 81747828 in words is "eighty-one million, seven hundred forty-seven thousand, eight hundred twenty-eight".