81259920 has 240 divisors, whose sum is σ = 325907712. Its totient is φ = 17740800.

The previous prime is 81259891. The next prime is 81259921. The reversal of 81259920 is 2995218.

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 (36).

It is not an unprimeable number, because it can be changed into a prime (81259921) 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, 115570 + ... + 116270.

Almost surely, 2^81259920 is an apocalyptic number.

81259920 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 81259920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (162953856).

81259920 is an abundant number, since it is smaller than the sum of its proper divisors (244647792).

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

81259920 is a wasteful number, since it uses less digits than its factorization.

81259920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750 (or 741 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 81259920 is about 9014.4284344599. The cubic root of 81259920 is about 433.1371788084.

The spelling of 81259920 in words is "eighty-one million, two hundred fifty-nine thousand, nine hundred twenty".