81185280 has 240 divisors, whose sum is σ = 292561632. Its totient is φ = 19046400.

The previous prime is 81185263. The next prime is 81185323. The reversal of 81185280 is 8258118.

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

It is a Harshad number since it is a multiple of its sum of digits (33).

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, 2618865 + ... + 2618895.

Almost surely, 2^81185280 is an apocalyptic number.

81185280 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 81185280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146280816).

81185280 is an abundant number, since it is smaller than the sum of its proper divisors (211376352).

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

81185280 is a wasteful number, since it uses less digits than its factorization.

81185280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99 (or 52 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 33.

The square root of 81185280 is about 9010.2874537941. The cubic root of 81185280 is about 433.0045211069.

The spelling of 81185280 in words is "eighty-one million, one hundred eighty-five thousand, two hundred eighty".