81241920 has 112 divisors (see below), whose sum is σ = 286633920. Its totient is φ = 21662208.

The previous prime is 81241907. The next prime is 81241931. The reversal of 81241920 is 2914218.

It is a Harshad number since it is a multiple of its sum of digits (27).

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, 3939 + ... + 13341.

Almost surely, 2^81241920 is an apocalyptic number.

81241920 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 81241920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (143316960).

81241920 is an abundant number, since it is smaller than the sum of its proper divisors (205392000).

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

81241920 is a wasteful number, since it uses less digits than its factorization.

81241920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9429 (or 9413 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 81241920 is about 9013.4299797580. The cubic root of 81241920 is about 433.1051948366.

The spelling of 81241920 in words is "eighty-one million, two hundred forty-one thousand, nine hundred twenty".