81809400 has 96 divisors (see below), whose sum is σ = 258019200. Its totient is φ = 21436800.

The previous prime is 81809363. The next prime is 81809411. The reversal of 81809400 is 490818.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

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, 34245 + ... + 36555.

It is an arithmetic number, because the mean of its divisors is an integer number (2687700).

Almost surely, 2^81809400 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81809400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (129009600).

81809400 is an abundant number, since it is smaller than the sum of its proper divisors (176209800).

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

81809400 is a wasteful number, since it uses less digits than its factorization.

81809400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2389 (or 2380 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 81809400 is about 9044.8548910416. The cubic root of 81809400 is about 434.1112784233. Note that the first 3 decimals are identical.

The spelling of 81809400 in words is "eighty-one million, eight hundred nine thousand, four hundred".