81240000 has 140 divisors (see below), whose sum is σ = 268995144. Its totient is φ = 21632000.

The previous prime is 81239999. The next prime is 81240007. The reversal of 81240000 is 4218.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81240007) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 119662 + ... + 120338.

Almost surely, 2^81240000 is an apocalyptic number.

81240000 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81240000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134497572).

81240000 is an abundant number, since it is smaller than the sum of its proper divisors (187755144).

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

81240000 is an equidigital number, since it uses as much as digits as its factorization.

81240000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 712 (or 687 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 81240000 is about 9013.3234713950. The cubic root of 81240000 is about 433.1017829341.

Adding to 81240000 its reverse (4218), we get a palindrome (81244218).

The spelling of 81240000 in words is "eighty-one million, two hundred forty thousand".