I could not find that catalog number in any of my references - 47720 would be the Sears part/ catalog item number of the bike - did find a 47772 as a 5 speed.
I'm pretty sure this bike left the factory as a multispeed model - hard to see in your photos, but.
1) any signs of washer markes where brakes may have been mounted ? Rear fender and brake bridge look to be the 'caliper brake' type, is the fork drilled for a brake ?
2) 5 speed chainring, you'd have to look and see if it's the narrower 3/32" ring, but odds are yes.
3) looks to be some wear marks on front of frame top tube where a shifter may have been at one point ? Also, are there marks on bars where brake levers might hvae been ?
4) stripes on seat tube - Sears had a habit of using number of stripes = speeds (24" spyder 5 speeds = 5 stripes, 10 have 10 stripes,etc - appears to be 5 stripes....
5) any sign it ever had a rear derailleur installed ? marks by axle nuts ?
6) rear rim is wrong - 36 spoke with small 'lip' on edge = modern / 90s replacment, so it's been swapped out
changed to a coaster sometime in it's life ?
The seat is wrong for sure, sissy bar looks right, a Persons type, circa 68-70 style, so dating concensus seems right on.
For my money, if the marks for brakes,etc seem present, I htink it was a 5 speed when new, will cost a few bucks to find pcs but worth the effort.
Can you post some closeup pics of the areas mentioned ? or describe findings and wear spots ?
NICE find for sure. Welcome to the club - warning, it's addicting.