1763

This number is a composite.

1763 = 41 × 43 = 42² − 1 equals the sum of the first 21 even-indexed primes (p₂ + p₄ + ⋯ + p₄₂), where 42 is the average of its twin prime factors. In base 42, its representation is (41, 41), a repdigit whose digits equal its smaller prime factor. It is a Brilliant number whose digit sum (17) and digit reversal (3671) are both prime. [Ahmed]