# 673

This number is a prime.

673 is the second prime to divide more than one number of the form p# - 1 (673 divides both 149# - 1 *and* 193# - 1).

673 divides 3333333331. [Benney]

The Louvre Pyramid is made up of 673 glass lozenges and triangles, not counting the doors.

Chlorophyll *a* fluoresces at 673 nanometers.

The smallest prime adjacent to any 3-perfect number. [Loungrides]

673 = 1(mod 6) = 1(mod 7)= 1(mod3). [Bergot]

There are 673 numbers N with no two same digits, having the property that when the sum of the k leftmost digits of N is divided by k the result is always an integer. [Post and Dale]

Professor David Broadhurst's favorite titanic prime is zeta(-673)/zeta(-1).

The only non-titanic prime of the form 337*2^n-1.

673 is the smallest multidigit prime as the reversal of the first K Fibonacci integers. In this case K=12, because 1+1+2+3+5+8+13+21+34+55+89+144 = 376. [Rivera]