import re
rpl = r'\geq \1'
# print(re.sub(r'\d+', rpl, 'Text 1')) # sre_constants.error: missing group name
# print(re.sub(r'\d+', r'some \1', 'Text 1')) # sre_constants.error: invalid group reference
print(re.sub(r'\d+', rpl.replace('\\', '\\\\'), 'Text 1'))