81520768 has 64 divisors (see below), whose sum is σ = 190699200. Its totient is φ = 33979392.

The previous prime is 81520757. The next prime is 81520781. The reversal of 81520768 is 86702518.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (37).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31923 + ... + 34381.

It is an arithmetic number, because the mean of its divisors is an integer number (2979675).

Almost surely, 2^81520768 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81520768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95349600).

81520768 is an abundant number, since it is smaller than the sum of its proper divisors (109178432).

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

81520768 is a wasteful number, since it uses less digits than its factorization.

81520768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2517 (or 2505 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 37.

The square root of 81520768 is about 9028.8852025042. The cubic root of 81520768 is about 433.6001470568.

It can be divided in two parts, 8 and 1520768, that multiplied together give a square (12166144 = 3488²).

The spelling of 81520768 in words is "eighty-one million, five hundred twenty thousand, seven hundred sixty-eight".