81510720 has 112 divisors (see below), whose sum is σ = 260713728. Its totient is φ = 21575680.

The previous prime is 81510719. The next prime is 81510721. The reversal of 81510720 is 2701518.

It is an interprime number because it is at equal distance from previous prime (81510719) and next prime (81510721).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81510721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 188905 + ... + 189335.

Almost surely, 2^81510720 is an apocalyptic number.

81510720 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 81510720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130356864).

81510720 is an abundant number, since it is smaller than the sum of its proper divisors (179203008).

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

81510720 is a wasteful number, since it uses less digits than its factorization.

81510720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 648 (or 638 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 24.

The square root of 81510720 is about 9028.3287489989. The cubic root of 81510720 is about 433.5823315831.

The spelling of 81510720 in words is "eighty-one million, five hundred ten thousand, seven hundred twenty".