81520080 has 80 divisors (see below), whose sum is σ = 260888064. Its totient is φ = 21035520.

The previous prime is 81520079. The next prime is 81520091. The reversal of 81520080 is 8002518.

It is a tau number, because it is divible by the number of its divisors (80).

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

It is a self number, because there is not a number n which added to its sum of digits gives 81520080.

It is a congruent number.

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, 1962 + ... + 12918.

Almost surely, 2^81520080 is an apocalyptic number.

81520080 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 81520080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130444032).

81520080 is an abundant number, since it is smaller than the sum of its proper divisors (179367984).

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

81520080 is a wasteful number, since it uses less digits than its factorization.

81520080 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11004 (or 10998 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 24.

The square root of 81520080 is about 9028.8471024821. The cubic root of 81520080 is about 433.5989272541.

Adding to 81520080 its reverse (8002518), we get a palindrome (89522598).

The spelling of 81520080 in words is "eighty-one million, five hundred twenty thousand, eighty".