5111111191

This number is a prime.

+ The number of consecutive composite numbers in the gap following the prime number 5111111191 is equal to the product of its digits. The sequence begins 11, 13, 151, 11113, 119131, 1111151, 11173111, 111111313, 111111571, 1311111313, 1311913111, 3111111511, 5111111191, ... . Can you find a larger term?

Copy/paste the following program to the left screen under "BASIC Program" at Quite BASIC and click on the triangular arrow above "Line:" at upper left to RUN:

05 REM "Length of Prime Gap" by Chuck Gaydos
10 INPUT "Enter an integer less than 10^12";N
20 IF INT(N)<>N THEN 10
30 GOSUB 220
40 IF F=0 THEN 70
50 PRINT N;" is a prime number!"
60 END
70 LET A=N
80 LET C=1
90 LET N=N+1
100 GOSUB 220
110 IF F=1 THEN 140
120 LET C=C+1
130 GOTO 90
140 LET N=A
150 LET N=N-1
160 GOSUB 220
170 IF F=1 THEN 200
180 LET C=C+1
190 GOTO 150
200 PRINT A;" is in a prime gap of length ";C;"."
210 END
220 LET F=0
230 IF N<2 THEN RETURN
240 LET F=1
250 IF N<4 THEN RETURN
260 LET F=0
270 IF N/2=INT(N/2) THEN RETURN
280 LET M=INT(SQR(N))
290 FOR O=3 TO M STEP 2
300 IF N/O<>INT(N/O) THEN 320
310 RETURN
320 NEXT O
330 LET F=1
340 RETURN

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