81406832640 has 832 divisors, whose sum is σ = 315918351360. Its totient is φ = 17505976320.

The previous prime is 81406832599. The next prime is 81406832671. The reversal of 81406832640 is 4623860418.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 81406832592 and 81406832601.

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, 760811467 + ... + 760811573.

Almost surely, 2^81406832640 is an apocalyptic number.

81406832640 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 81406832640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (157959175680).

81406832640 is an abundant number, since it is smaller than the sum of its proper divisors (234511518720).

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

81406832640 is a wasteful number, since it uses less digits than its factorization.

81406832640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236 (or 214 counting only the distinct ones).

The product of its (nonzero) digits is 221184, while the sum is 42.

The spelling of 81406832640 in words is "eighty-one billion, four hundred six million, eight hundred thirty-two thousand, six hundred forty".