LAS VEGAS — Soon-to-be newlyweds lined up out the door of the marriage license office in Las Vegas on Friday, ahead of a unique date to tie the knot: 4/3/21.

Nearly 700 couples obtained licenses for the Saturday date, said Jeff Klein, a spokesman for the Clark County Marriage Bureau, as the city where Elvis can be part of the wedding party got set to mark yet another quirky date for nuptials. The clerk's office marked the occasion with keepsake marriage certificates.

"Specialty dates like 4/3/21 are always immensely popular," said county Clerk Lynn Goya, who noted that more than 1,800 couples were married on Dec. 13, 2014.

April is usually busy for weddings, and past dates with notable numeric sequences have tallied more than 1,000 weddings in a day, Goya said.

The office is bracing for a busy first 10 days this December, offering what the clerk dubs "palindrome days" for numbers reading the same forward and backward. 

Nearly 2,700 couples married on 10/10/10; more than 1,800 tied the knot on 12/12/12; and 3,125 were wed on 11/11/11. 

The most popular date to date?

Goya said 7/7/7 took the cake, with 4,492 marriages.