81816880 has 40 divisors (see below), whose sum is σ = 190603872. Its totient is φ = 32661504.

The previous prime is 81816871. The next prime is 81816883. The reversal of 81816880 is 8861818.

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (81816883) 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 7 ways as a sum of consecutive naturals, for example, 70384 + ... + 71536.

Almost surely, 2^81816880 is an apocalyptic number.

81816880 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81816880 is an abundant number, since it is smaller than the sum of its proper divisors (108786992).

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

81816880 is a wasteful number, since it uses less digits than its factorization.

81816880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2053 (or 2047 counting only the distinct ones).

The product of its (nonzero) digits is 24576, while the sum is 40.

The square root of 81816880 is about 9045.2683763391. The cubic root of 81816880 is about 434.1245085794.

The spelling of 81816880 in words is "eighty-one million, eight hundred sixteen thousand, eight hundred eighty".