thus
Sum (digits (1679,10)) = 23
by Th1046; NUMBER11:def 1 ( 23 divides 1679 & ( for m being Nat st Sum (digits (m,10)) = 23 & 23 divides m holds
1679 <= m ) )
1679 = 73 * 23
;
hence
23 divides 1679
by INT_1:def 3; for m being Nat st Sum (digits (m,10)) = 23 & 23 divides m holds
1679 <= m
let m be Nat; ( Sum (digits (m,10)) = 23 & 23 divides m implies 1679 <= m )
assume A1:
( Sum (digits (m,10)) = 23 & 23 divides m )
; 1679 <= m
then consider j being Nat such that
A2:
m = 23 * j
by NAT_D:def 3;
assume
m < 1679
; contradiction
then
23 * j < 23 * 73
by A2;
then
j < 72 + 1
by XREAL_1:64;
then
j <= 72
by NAT_1:9;
then
not not j = 0 & ... & not j = 72
;
per cases then
( j = 0 or j = 1 or j = 2 or j = 3 or j = 4 or j = 5 or j = 6 or j = 7 or j = 8 or j = 9 or j = 10 or j = 11 or j = 12 or j = 13 or j = 14 or j = 15 or j = 16 or j = 17 or j = 18 or j = 19 or j = 20 or j = 21 or j = 22 or j = 23 or j = 24 or j = 25 or j = 26 or j = 27 or j = 28 or j = 29 or j = 30 or j = 31 or j = 32 or j = 33 or j = 34 or j = 35 or j = 36 or j = 37 or j = 38 or j = 39 or j = 40 or j = 41 or j = 42 or j = 43 or j = 44 or j = 45 or j = 46 or j = 47 or j = 48 or j = 49 or j = 50 or j = 51 or j = 52 or j = 53 or j = 54 or j = 55 or j = 56 or j = 57 or j = 58 or j = 59 or j = 60 or j = 61 or j = 62 or j = 63 or j = 64 or j = 65 or j = 66 or j = 67 or j = 68 or j = 69 or j = 70 or j = 71 or j = 72 )
;
end;