81955994400 has 360 divisors, whose sum is σ = 341576262720. Its totient is φ = 18732695040.

The previous prime is 81955994387. The next prime is 81955994453. The reversal of 81955994400 is 449955918.

81955994400 is a `hidden beast` number, since 8 + 1 + 9 + 5 + 599 + 4 + 40 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (360).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 363261 + ... + 543939.

It is an arithmetic number, because the mean of its divisors is an integer number (948822952).

Almost surely, 2^81955994400 is an apocalyptic number.

81955994400 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 81955994400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (170788131360).

81955994400 is an abundant number, since it is smaller than the sum of its proper divisors (259620268320).

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

81955994400 is a wasteful number, since it uses less digits than its factorization.

81955994400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180718 (or 180696 counting only the distinct ones).

The product of its (nonzero) digits is 2332800, while the sum is 54.

The spelling of 81955994400 in words is "eighty-one billion, nine hundred fifty-five million, nine hundred ninety-four thousand, four hundred".