9173

This number is a prime.

The largest emirp formed with the four digits that can end multidigit primes. [Loungrides]

The largest left-truncatable prime (emirp) consisted of only odd distinct digits. [Loungrides]

The larger of only two emirps with distinct digits in English alphabetical order (Nine, One, Seven, Three). The other is 73. [Loungrides]

The largest prime (emirp) concatenated from two double-digit numbers, i.e., 91 and 73, having the same sum of digits. [Loungrides]

The last known term corresponding to a(1)-a(22) in OEIS A390417. The sequence begins 3719, 3791, 7319, 7391, 7931, 7913, 3179, 3971, 7139, 9731, 3917, 3197, 9371, 1739, 1379, 7193, 1397, 9317, 9137, 9713, 1793, 9173. Found by Ben Chaffin in May 2026.