| Base | Representation |
|---|---|
| bin | 100101101101111111… |
| … | …0011110101000000000 |
| 3 | 21202002000210100010000 |
| 4 | 1023123332132220000 |
| 5 | 2311342000000000 |
| 6 | 101113315040000 |
| 7 | 5565153432333 |
| oct | 1133376365000 |
| 9 | 252060710100 |
| 10 | 81000000000 |
| 11 | 3139642a967 |
| 12 | 138468a0000 |
| 13 | 783b371caa |
| 14 | 3cc58c661a |
| 15 | 21911a0000 |
| hex | 12dbf9ea00 |
81000000000 has 500 divisors, whose sum is σ = 302204558898. Its totient is φ = 21600000000.
The previous prime is 80999999981. The next prime is 81000000047. The reversal of 81000000000 is 18.
It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.
It can be written as a sum of positive squares in 5 ways, for example, as 76202498304 + 4797501696 = 276048^2 + 69264^2 .
It is a tau number, because it is divible by the number of its divisors (500).
It is an ABA number since it can be written as A⋅BA, here for A=3, B=3000.
It is a super-2 number, since 2×810000000002 (a number of 23 digits) contains 22 as substring.
It is a Harshad number since it is a multiple of its sum of digits (9).
It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.
It is a nialpdrome in base 10.
It is an unprimeable number.
It is a pernicious number, because its binary representation contains a prime number (19) of ones.
It is a polite number, since it can be written in 49 ways as a sum of consecutive naturals, for example, 16199999998 + ... + 16200000002.
Almost surely, 281000000000 is an apocalyptic number.
81000000000 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 81000000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (151102279449).
81000000000 is an abundant number, since it is smaller than the sum of its proper divisors (221204558898).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
81000000000 is an frugal number, since it uses more digits than its factorization.
81000000000 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 75 (or 10 counting only the distinct ones).
The product of its (nonzero) digits is 8, while the sum is 9.
Adding to 81000000000 its reverse (18), we get a palindrome (81000000018).
The spelling of 81000000000 in words is "eighty-one billion", and thus it is an aban number and an uban number.
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