81781257600 has 576 divisors, whose sum is σ = 338131379040. Its totient is φ = 18433474560.

The previous prime is 81781257589. The next prime is 81781257601. The reversal of 81781257600 is 675218718.

It is a happy number.

81781257600 is a `hidden beast` number, since 8 + 1 + 78 + 1 + 2 + 576 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81781257601) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 14714022 + ... + 14719578.

Almost surely, 2^81781257600 is an apocalyptic number.

81781257600 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 81781257600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (169065689520).

81781257600 is an abundant number, since it is smaller than the sum of its proper divisors (256350121440).

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

81781257600 is a wasteful number, since it uses less digits than its factorization.

81781257600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5667 (or 5647 counting only the distinct ones).

The product of its (nonzero) digits is 188160, while the sum is 45.

The spelling of 81781257600 in words is "eighty-one billion, seven hundred eighty-one million, two hundred fifty-seven thousand, six hundred".