abcd+abc+ab+a=3749
1111a+111b+11c+d=3749
1111a≤3749
a≤3
b、c、d最多只能取9
1111a+111×9+11×9+9≥3749
1111a≥2642
a≥3
综上,得a=3
111b+11c+d=3749-1111×3=416
111b≤416 b≤3
c、d至多取9
111b+11×9+9≥416
111b≥308
b≥3
综上,得b=3
11c+d=416-111×3=83
11c≤83 c≤7
d至多取9 11c+9≥83
11c≥74
c≥7
综上,得c=7
d=83-11×7=6
综上,得a=3 b=3 c=7 d=6,所求数为3376