47 is a Prime Number
47 = 1 × 23 + 4 + 5 + 6 + 7 + 8 + 9
47 = 98 − 76 + 5 − 4 + 3 + 21
47 = 0^4 + 1^9 + 2^8 + 3^5 − 4^7 + 5^6 + 6^3 + 7^0 + 8^1 + 9^2
47, smallest number with 9 representations as a sum of 3 distinct primes: 47 = 3 + 7 + 37 = 3 + 13 + 31 = 5 + 11 + 31 = 5 + 13 + 29 = 5 + 19 + 23 = 7 + 11 + 29 = 7 + 17 + 23 = 11 + 13 + 23 = 11 + 17 + 19
Prime p such that (p-1)/2 and (p-3)/4 are also prime.
Safe prime p: (p-1)/2 is also prime.
Sexy Prime (Primes p such that p + 6 is also prime)
Number of fractions in Farey series of order 12: 0/1, 1/12, 1/11, 1/10, 1/9, 1/8, 1/7, 1/6, 2/11, 1/5, 2/9, 1/4, 3/11, 2/7, 3/10, 1/3, 4/11, 3/8, 2/5, 5/12, 3/7, 4/9, 5/11, 1/2, 6/11, 5/9, 4/7, 7/12, 3/5, 5/8, 7/11, 2/3, 7/10, 5/7, 8/11, 3/4, 7/9, 4/5, 9/11, 5/6, 6/7, 7/8, 8/9, 9/10, 10/11, 11/12, 1/1
47 + 2 = 49 and 47 * 2 = 94
\( 47^9 = 1^9+2^9+4^9+7^9+11^9+14^9+15^9+18^9+26^9+27^9+30^9+31^9+32^9+33^9 +36^9+38^9+39^9+43^9 \)
Numbers k such that 2^k + 9 is prime
Number of ways of arranging 5 lines in the affine plane.
Part of the Cunningham chain 2, 5, 11, 23, 47
47 cannot be written as a sum of 3 squares. (Integers that are not a sum of three squares)
The ring of integers of the field Q(sqrt(-47)) has class number 5.
Prime whose binary representation is also the decimal representation of a prime.
Keith number or Repfigit (Repetitive Fibonacci-like digit)
Factors: 1, 47
Forty-seven
Representations, Binary to Hexadecimal:
101111_2
1202_3
233_4
142_5
115_6
65_7
57_8
52_9
43_11
3b_12
38_13
35_14
32_15
2f_16
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