81209880 has 48 divisors (see below), whose sum is σ = 263933280. Its totient is φ = 21655872.

The previous prime is 81209873. The next prime is 81209881. The reversal of 81209880 is 8890218.

It is a super-2 number, since 2×81209880² = 13190089219228800, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81209881) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 112432 + ... + 113151.

It is an arithmetic number, because the mean of its divisors is an integer number (5498610).

Almost surely, 2^81209880 is an apocalyptic number.

It is an amenable number.

81209880 is an abundant number, since it is smaller than the sum of its proper divisors (182723400).

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

81209880 is a wasteful number, since it uses less digits than its factorization.

81209880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 225600 (or 225593 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 81209880 is about 9011.6524566807. The cubic root of 81209880 is about 433.0482516761.

The spelling of 81209880 in words is "eighty-one million, two hundred nine thousand, eight hundred eighty".