81356400 has 270 divisors, whose sum is σ = 302630432. Its totient is φ = 20995200.

The previous prime is 81356399. The next prime is 81356411. The reversal of 81356400 is 465318.

81356400 is a `hidden beast` number, since 8 + 13 + 5 + 640 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (270).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

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 53 ways as a sum of consecutive naturals, for example, 2624385 + ... + 2624415.

Almost surely, 2^81356400 is an apocalyptic number.

81356400 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 81356400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (151315216).

81356400 is an abundant number, since it is smaller than the sum of its proper divisors (221274032).

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

81356400 is an equidigital number, since it uses as much as digits as its factorization.

81356400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73 (or 41 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 81356400 is about 9019.7782677846. The cubic root of 81356400 is about 433.3085324399.

It can be divided in two parts, 8135 and 6400, that added together give a triangular number (14535 = T₁₇₀).

The spelling of 81356400 in words is "eighty-one million, three hundred fifty-six thousand, four hundred".