81640080 has 120 divisors (see below), whose sum is σ = 276377400. Its totient is φ = 21596160.

The previous prime is 81640079. The next prime is 81640099. The reversal of 81640080 is 8004618.

It can be written as a sum of positive squares in 4 ways, for example, as 5531904 + 76108176 = 2352^2 + 8724^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 106900 + ... + 107660.

It is an arithmetic number, because the mean of its divisors is an integer number (2303145).

Almost surely, 2^81640080 is an apocalyptic number.

81640080 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 81640080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (138188700).

81640080 is an abundant number, since it is smaller than the sum of its proper divisors (194737320).

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

81640080 is a wasteful number, since it uses less digits than its factorization.

81640080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 929 (or 920 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 81640080 is about 9035.4900254496. The cubic root of 81640080 is about 433.8115798149.

Adding to 81640080 its reverse (8004618), we get a palindrome (89644698).

The spelling of 81640080 in words is "eighty-one million, six hundred forty thousand, eighty".