81788820 has 48 divisors (see below), whose sum is σ = 229403328. Its totient is φ = 21772800.

The previous prime is 81788797. The next prime is 81788821. The reversal of 81788820 is 2888718.

It is a happy number.

It is a super-2 number, since 2×81788820² = 13378822153984800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81788821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 62412 + ... + 63708.

It is an arithmetic number, because the mean of its divisors is an integer number (4779236).

Almost surely, 2^81788820 is an apocalyptic number.

It is an amenable number.

81788820 is an abundant number, since it is smaller than the sum of its proper divisors (147614508).

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

81788820 is a wasteful number, since it uses less digits than its factorization.

81788820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2360 (or 2358 counting only the distinct ones).

The product of its (nonzero) digits is 57344, while the sum is 42.

The square root of 81788820 is about 9043.7171561256. The cubic root of 81788820 is about 434.0748736444.

The spelling of 81788820 in words is "eighty-one million, seven hundred eighty-eight thousand, eight hundred twenty".