All strange numbers are prime. Every one digit prime number is
strange and a number of two or more digits is strange if and only
if so are the two numbers obtained from it by omitting either its
first or its last digit. Find all strange numbers.
One to Eight
Age 11 to 14 Challenge Level:
Expressing the four digit numbers as the product of their prime
factors may help you narrow down the options.
The units digit of the factors will determine the units digit of
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice.