81563166720 has 864 divisors, whose sum is σ = 339136761600. Its totient is φ = 17757831168.

The previous prime is 81563166701. The next prime is 81563166721. The reversal of 81563166720 is 2766136518.

81563166720 is a `hidden beast` number, since 8 + 1 + 5 + 631 + 6 + 6 + 7 + 2 + 0 = 666.

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

It is not an unprimeable number, because it can be changed into a prime (81563166721) 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, 341268361 + ... + 341268599.

It is an arithmetic number, because the mean of its divisors is an integer number (392519400).

Almost surely, 2^81563166720 is an apocalyptic number.

81563166720 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 81563166720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (169568380800).

81563166720 is an abundant number, since it is smaller than the sum of its proper divisors (257573594880).

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

81563166720 is a wasteful number, since it uses less digits than its factorization.

81563166720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325 (or 279 counting only the distinct ones).

The product of its (nonzero) digits is 362880, while the sum is 45.

The spelling of 81563166720 in words is "eighty-one billion, five hundred sixty-three million, one hundred sixty-six thousand, seven hundred twenty".