81438720 has 192 divisors, whose sum is σ = 285405120. Its totient is φ = 19660800.

The previous prime is 81438683. The next prime is 81438787. The reversal of 81438720 is 2783418.

It is a tau number, because it is divible by the number of its divisors (192).

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 337800 + ... + 338040.

It is an arithmetic number, because the mean of its divisors is an integer number (1486485).

Almost surely, 2^81438720 is an apocalyptic number.

81438720 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 81438720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142702560).

81438720 is an abundant number, since it is smaller than the sum of its proper divisors (203966400).

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

81438720 is a wasteful number, since it uses less digits than its factorization.

81438720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 282 (or 262 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 33.

The square root of 81438720 is about 9024.3404191110. The cubic root of 81438720 is about 433.4546300808.

The spelling of 81438720 in words is "eighty-one million, four hundred thirty-eight thousand, seven hundred twenty".