81788020 has 48 divisors (see below), whose sum is σ = 182701008. Its totient is φ = 30648320.

The previous prime is 81788011. The next prime is 81788087. The reversal of 81788020 is 2088718.

It can be written as a sum of positive squares in 8 ways, for example, as 4418404 + 77369616 = 2102^2 + 8796^2 .

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 99210 + ... + 100030.

It is an arithmetic number, because the mean of its divisors is an integer number (3806271).

Almost surely, 2^81788020 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81788020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (91350504).

81788020 is an abundant number, since it is smaller than the sum of its proper divisors (100912988).

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

81788020 is a wasteful number, since it uses less digits than its factorization.

81788020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1140 (or 1138 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 34.

The square root of 81788020 is about 9043.6729264166. The cubic root of 81788020 is about 434.0734583693.

The spelling of 81788020 in words is "eighty-one million, seven hundred eighty-eight thousand, twenty".