81225840 has 80 divisors (see below), whose sum is σ = 254233728. Its totient is φ = 21451008.

The previous prime is 81225791. The next prime is 81225853. The reversal of 81225840 is 4852218.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81225798 and 81225807.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24099 + ... + 27261.

Almost surely, 2^81225840 is an apocalyptic number.

81225840 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 81225840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (127116864).

81225840 is an abundant number, since it is smaller than the sum of its proper divisors (173007888).

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

81225840 is a wasteful number, since it uses less digits than its factorization.

81225840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3286 (or 3280 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 30.

The square root of 81225840 is about 9012.5379333460. The cubic root of 81225840 is about 433.0766184930.

The spelling of 81225840 in words is "eighty-one million, two hundred twenty-five thousand, eight hundred forty".