81647978892480 has 5376 divisors, whose sum is σ = 414249780510720. Its totient is φ = 14852881612800.

The previous prime is 81647978892463. The next prime is 81647978892499. The reversal of 81647978892480 is 8429887974618.

81647978892480 is a `hidden beast` number, since 8 + 1 + 6 + 47 + 9 + 7 + 8 + 8 + 92 + 480 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 81647978892480.

It is an unprimeable number.

It is a polite number, since it can be written in 767 ways as a sum of consecutive naturals, for example, 265954328487 + ... + 265954328793.

It is an arithmetic number, because the mean of its divisors is an integer number (77055390720).

Almost surely, 2^{81647978892480} is an apocalyptic number.

81647978892480 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 81647978892480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (207124890255360).

81647978892480 is an abundant number, since it is smaller than the sum of its proper divisors (332601801618240).

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

81647978892480 is a wasteful number, since it uses less digits than its factorization.

81647978892480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 585 (or 562 counting only the distinct ones).

The product of its (nonzero) digits is 3121348608, while the sum is 81.

The spelling of 81647978892480 in words is "eighty-one trillion, six hundred forty-seven billion, nine hundred seventy-eight million, eight hundred ninety-two thousand, four hundred eighty".