81218880 has 84 divisors (see below), whose sum is σ = 279369012. Its totient is φ = 21657600.

The previous prime is 81218801. The next prime is 81218897. The reversal of 81218880 is 8881218.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 41679936 + 39538944 = 6456^2 + 6288^2 .

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11221 + ... + 16980.

Almost surely, 2^81218880 is an apocalyptic number.

81218880 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81218880 is an abundant number, since it is smaller than the sum of its proper divisors (198150132).

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

81218880 is a wasteful number, since it uses less digits than its factorization.

81218880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28224 (or 28211 counting only the distinct ones).

The product of its (nonzero) digits is 8192, while the sum is 36.

The square root of 81218880 is about 9012.1517963248. The cubic root of 81218880 is about 433.0642484584.

The spelling of 81218880 in words is "eighty-one million, two hundred eighteen thousand, eight hundred eighty".