81841680 has 120 divisors (see below), whose sum is σ = 276725592. Its totient is φ = 21676032.

The previous prime is 81841663. The next prime is 81841703. The reversal of 81841680 is 8614818.

It can be written as a sum of positive squares in 4 ways, for example, as 57517056 + 24324624 = 7584^2 + 4932^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 141552 + ... + 142128.

Almost surely, 2^81841680 is an apocalyptic number.

81841680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81841680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (138362796).

81841680 is an abundant number, since it is smaller than the sum of its proper divisors (194883912).

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

81841680 is a wasteful number, since it uses less digits than its factorization.

81841680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 793 (or 784 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 36.

The square root of 81841680 is about 9046.6391549569. The cubic root of 81841680 is about 434.1683675003.

The spelling of 81841680 in words is "eighty-one million, eight hundred forty-one thousand, six hundred eighty".