81311400 has 144 divisors (see below), whose sum is σ = 275652000. Its totient is φ = 21479040.

The previous prime is 81311383. The next prime is 81311423. The reversal of 81311400 is 411318.

It is a super-2 number, since 2×81311400² = 13223087539920000, which contains 22 as substring.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 358087 + ... + 358313.

It is an arithmetic number, because the mean of its divisors is an integer number (1914250).

Almost surely, 2^81311400 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 81311400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137826000).

81311400 is an abundant number, since it is smaller than the sum of its proper divisors (194340600).

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

81311400 is a wasteful number, since it uses less digits than its factorization.

81311400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448 (or 436 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 81311400 is about 9017.2834046624. The cubic root of 81311400 is about 433.2286269043.

Adding to 81311400 its reverse (411318), we get a palindrome (81722718).

The spelling of 81311400 in words is "eighty-one million, three hundred eleven thousand, four hundred".