81445680 has 240 divisors, whose sum is σ = 292481280. Its totient is φ = 20275200.

The previous prime is 81445667. The next prime is 81445687. The reversal of 81445680 is 8654418.

It is a tau number, because it is divible by the number of its divisors (240).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

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 (81445687) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 915076 + ... + 915164.

It is an arithmetic number, because the mean of its divisors is an integer number (1218672).

Almost surely, 2^81445680 is an apocalyptic number.

81445680 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 81445680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146240640).

81445680 is an abundant number, since it is smaller than the sum of its proper divisors (211035600).

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

81445680 is a wasteful number, since it uses less digits than its factorization.

81445680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180 (or 171 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The square root of 81445680 is about 9024.7260346229. The cubic root of 81445680 is about 433.4669778448.

It can be divided in two parts, 8144 and 5680, that added together give a cube (13824 = 24³).

The spelling of 81445680 in words is "eighty-one million, four hundred forty-five thousand, six hundred eighty".