## EPORNAn equal product of reversible numbers; defined by the
Indian recreational mathematician Shyam Sunder Gupta as a number that can
be expressed as the product of two reversible numbers (numbers whose digits
are reversed) in two different ways. For example: 4,030 = 130 × 031
= 310 × 013 and 144,648 = 861 × 168 = 492 × 294. The smallest
EPORN, 2,520 = 120 × 021 = 210 × 012, is also the least
common multiple of all single digit natural numbers in the decimal system.
The digital root, i.e. the ultimate
sum of digits, of all EPORNs is always 1, 4, 7, or 9. For example, 2,520
= 2 + 5 + 2 + 0 = 9; 4,030 = 4 + 0 + 3 + 0 = 7; 9,949,716 = 9 + 9 + 4 +
9 + 7 + 1 + 6 = 36 and 3 + 6 = 9. ## Reference- Gupta, S. S. "EPORNS",
*Science Today*, February 1987, India.
## Related category• TYPES OF NUMBERS | |||||

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