81522720 has 192 divisors, whose sum is σ = 289578240. Its totient is φ = 21417984.

The previous prime is 81522709. The next prime is 81522731. The reversal of 81522720 is 2722518.

It is an interprime number because it is at equal distance from previous prime (81522709) and next prime (81522731).

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

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 488077 + ... + 488243.

It is an arithmetic number, because the mean of its divisors is an integer number (1508220).

Almost surely, 2^81522720 is an apocalyptic number.

81522720 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 81522720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144789120).

81522720 is an abundant number, since it is smaller than the sum of its proper divisors (208055520).

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

81522720 is a wasteful number, since it uses less digits than its factorization.

81522720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304 (or 290 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 81522720 is about 9028.9932993662. The cubic root of 81522720 is about 433.6036078548.

The spelling of 81522720 in words is "eighty-one million, five hundred twenty-two thousand, seven hundred twenty".