81751680 has 320 divisors, whose sum is σ = 311018400. Its totient is φ = 20404224.

The previous prime is 81751613. The next prime is 81751687. The reversal of 81751680 is 8615718.

It is a tau number, because it is divible by the number of its divisors (320).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81751687) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 984919 + ... + 985001.

Almost surely, 2^81751680 is an apocalyptic number.

81751680 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 81751680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (155509200).

81751680 is an abundant number, since it is smaller than the sum of its proper divisors (229266720).

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

81751680 is a wasteful number, since it uses less digits than its factorization.

81751680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133 (or 112 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 36.

The square root of 81751680 is about 9041.6635637475. The cubic root of 81751680 is about 434.0091597662.

The spelling of 81751680 in words is "eighty-one million, seven hundred fifty-one thousand, six hundred eighty".