81331200 has 198 divisors, whose sum is σ = 292029114. Its totient is φ = 21626880.

The previous prime is 81331177. The next prime is 81331231. The reversal of 81331200 is 213318.

It can be written as a sum of positive squares in 3 ways, for example, as 3326976 + 78004224 = 1824^2 + 8832^2 .

It is a super-2 number, since 2×81331200² = 13229528186880000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 230224 + ... + 230576.

Almost surely, 2^81331200 is an apocalyptic number.

81331200 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 81331200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146014557).

81331200 is an abundant number, since it is smaller than the sum of its proper divisors (210697914).

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

81331200 is a wasteful number, since it uses less digits than its factorization.

81331200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 389 (or 363 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 81331200 is about 9018.3812294668. The cubic root of 81331200 is about 433.2637889711.

Adding to 81331200 its reverse (213318), we get a palindrome (81544518).

The spelling of 81331200 in words is "eighty-one million, three hundred thirty-one thousand, two hundred".