Base | Representation |
---|---|
bin | 100011101101… |
… | …1000010100101 |
3 | 1022020020002202 |
4 | 1013123002211 |
5 | 14243113411 |
6 | 1505144245 |
7 | 315066644 |
oct | 107330245 |
9 | 38206082 |
10 | 18722981 |
11 | a628942 |
12 | 632b085 |
13 | 3b570b4 |
14 | 26b535b |
15 | 199c83b |
hex | 11db0a5 |
18722981 has 2 divisors, whose sum is σ = 18722982. Its totient is φ = 18722980.
The previous prime is 18722947. The next prime is 18722983. The reversal of 18722981 is 18922781.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 17850625 + 872356 = 4225^2 + 934^2 .
It is an emirp because it is prime and its reverse (18922781) is a distict prime.
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-18722981 is a prime.
It is a super-2 number, since 2×187229812 = 701100035052722, which contains 22 as substring.
It is a Sophie Germain prime.
Together with 18722983, it forms a pair of twin primes.
It is a Chen prime.
It is a Curzon number.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (18722983) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9361490 + 9361491.
It is an arithmetic number, because the mean of its divisors is an integer number (9361491).
Almost surely, 218722981 is an apocalyptic number.
It is an amenable number.
18722981 is a deficient number, since it is larger than the sum of its proper divisors (1).
18722981 is an equidigital number, since it uses as much as digits as its factorization.
18722981 is an evil number, because the sum of its binary digits is even.
The product of its digits is 16128, while the sum is 38.
The square root of 18722981 is about 4327.0060087779. The cubic root of 18722981 is about 265.5369721873.
The spelling of 18722981 in words is "eighteen million, seven hundred twenty-two thousand, nine hundred eighty-one".
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