81891077760 has 512 divisors, whose sum is σ = 300983558400. Its totient is φ = 21290065920.

The previous prime is 81891077729. The next prime is 81891077783. The reversal of 81891077760 is 6777019818.

It is a super-2 number, since 2×81891077760² (a number of 23 digits) contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 81891077697 and 81891077706.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 57386167 + ... + 57387593.

Almost surely, 2^81891077760 is an apocalyptic number.

81891077760 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 81891077760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (150491779200).

81891077760 is an abundant number, since it is smaller than the sum of its proper divisors (219092480640).

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

81891077760 is an equidigital number, since it uses as much as digits as its factorization.

81891077760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1508 (or 1478 counting only the distinct ones).

The product of its (nonzero) digits is 1185408, while the sum is 54.

The spelling of 81891077760 in words is "eighty-one billion, eight hundred ninety-one million, seventy-seven thousand, seven hundred sixty".