81409500 has 144 divisors (see below), whose sum is σ = 261206400. Its totient is φ = 21340800.

The previous prime is 81409487. The next prime is 81409511. The reversal of 81409500 is 590418.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 355386 + ... + 355614.

Almost surely, 2^81409500 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 81409500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130603200).

81409500 is an abundant number, since it is smaller than the sum of its proper divisors (179796900).

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

81409500 is a wasteful number, since it uses less digits than its factorization.

81409500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333 (or 318 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 81409500 is about 9022.7213189813. The cubic root of 81409500 is about 433.4027830831.

Adding to 81409500 its reverse (590418), we get a palindrome (81999918).

The spelling of 81409500 in words is "eighty-one million, four hundred nine thousand, five hundred".