81481680 has 320 divisors, whose sum is σ = 340692480. Its totient is φ = 17473536.

The previous prime is 81481669. The next prime is 81481703. The reversal of 81481680 is 8618418.

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 an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 256882 + ... + 257198.

It is an arithmetic number, because the mean of its divisors is an integer number (1064664).

Almost surely, 2^81481680 is an apocalyptic number.

81481680 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 81481680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (170346240).

81481680 is an abundant number, since it is smaller than the sum of its proper divisors (259210800).

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

81481680 is a wasteful number, since it uses less digits than its factorization.

81481680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363 (or 351 counting only the distinct ones).

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

The square root of 81481680 is about 9026.7203346509. The cubic root of 81481680 is about 433.5308343628.

The spelling of 81481680 in words is "eighty-one million, four hundred eighty-one thousand, six hundred eighty".