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Seven

Seven (7) is the natural number following six and preceding eight.

Seven is the fourth-smallest prime number; the next is eleven. Seven is a Mersenne prime. This is because 23-1=7, and seven is a prime number.

7 goes into 999,999 exactly 142,857 times, so fractions with 7 in the denominator have six-digit repeating sequences in their decimal expansions. 1/7=0.142857142...

A seven-sided polygon is a heptagon[?]. The regular n-gons for n ≤ 6 can be constructed by ruler and compass alone, but the regular heptagon cannot.

The British fifty-pence coin is a heptagon, with the sides curved to give it a constant radius.

Cities constructed amidst seven hills include:

Seven is also:



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List of all two-letter combinations

... QB[?] QC QD[?] QE[?] QF[?] QG[?] QH[?] QI[?] QJ[?] QK[?] QL[?] QM[?] QN[?] QO[?] QP[?] QQ[?] QR[?] QS[?] QT[?] QU[?] QV[?] QW[?] QX[?] QY[?] QZ[?] RA[?] RB[?] RC RD[?] ...