81162890640 has 120 divisors (see below), whose sum is σ = 293539155000. Its totient is φ = 19978555392.

The previous prime is 81162890629. The next prime is 81162890657. The reversal of 81162890640 is 4609826118.

81162890640 is a `hidden beast` number, since 8 + 11 + 628 + 9 + 0 + 6 + 4 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 17652842496 + 63510048144 = 132864^2 + 252012^2 .

It is a tau number, because it is divible by the number of its divisors (120).

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

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4326265 + ... + 4344984.

It is an arithmetic number, because the mean of its divisors is an integer number (2446159625).

Almost surely, 2^81162890640 is an apocalyptic number.

81162890640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81162890640 is an abundant number, since it is smaller than the sum of its proper divisors (212376264360).

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

81162890640 is a wasteful number, since it uses less digits than its factorization.

81162890640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8671281 (or 8671272 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 45.

The spelling of 81162890640 in words is "eighty-one billion, one hundred sixty-two million, eight hundred ninety thousand, six hundred forty".