81502720 has 160 divisors (see below), whose sum is σ = 219985920. Its totient is φ = 28753920.

The previous prime is 81502717. The next prime is 81502727. The reversal of 81502720 is 2720518.

It is a tau number, because it is divible by the number of its divisors (160).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81502727) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1031641 + ... + 1031719.

It is an arithmetic number, because the mean of its divisors is an integer number (1374912).

Almost surely, 2^81502720 is an apocalyptic number.

81502720 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 81502720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109992960).

81502720 is an abundant number, since it is smaller than the sum of its proper divisors (138483200).

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

81502720 is a wasteful number, since it uses less digits than its factorization.

81502720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 25.

The square root of 81502720 is about 9027.8856882440. The cubic root of 81502720 is about 433.5681462418.

The spelling of 81502720 in words is "eighty-one million, five hundred two thousand, seven hundred twenty".