Superstition could play a role in street numbers Rotorua people choose to live at.
Homes.co.nz, which publishes sales histories and values, has analysed the relationship between letterbox numbers under 20 and house values.
Rotorua's least valuable letterbox number was two, worth an estimated median of $280,000.
The next lowest valued number was one, followed by number 13.
The most valuable street number in Rotorua was five, with a median estimated value of $325,000. The next most valuable numbers were 18 and 12.
Numbers six, eight and nine are considered lucky in Chinese culture. Those numbers were valued slightly more highly than the number four in Rotorua, which is considered unlucky in the culture.
LJ Hooker Rotorua principal Malcolm Forsyth said he'd heard some cultures were averse to some numbers but hadn't had too much experience with people being put off by a digit on the letterbox.
"I think certain people might get put off by certain things but overall I don't think it's a major problem."
Living near an intersection could have been a factor in reducing values for numbers one and two, he said.
However, he'd also come across people who wanted to buy properties near intersections because they were busy. Sometimes people living on their own might like to have activity around them.
Mr Forsyth said feng shui, or the flow of a place, was a factor for buyers from some cultures.
Sometimes people would just say a house didn't feel right.
"Apart from that, I think most people are looking for certain properties in a certain area in a certain price bracket and the address or the number on the letterbox is probably a little bit down on the list of priorities," said Mr Forsyth.
Ross Stanway, chief executive of Eves and Bayleys Real Estate, said any property-related superstitions he came across tended to be culturally driven.
They were more relevant in Asian and Southeast Asian cultures than in the Kiwi culture.
"I would imagine certainly in the Auckland market it's far more prevalent and probably quite real in terms of its impact."
He said some buyers also considered street appeal and the configuration of a house.
He hadn't come across any New Zealanders who had been reluctant to buy at number 13.
"I think the house behind the number is what they want. That's what they're interested in," said Mr Stanway.
Homes.co.nz spokesman Jeremy O'Hanlon said the idea that a number on a letterbox could impact values was a little absurd. However, number 13 seemed to drive down values in certain regions.
"It's funny that Whangarei seems to buck the trend and value 13 higher than all but the number 12. While the Bay of Plenty and Hawkes Bay seem to have a real distaste for it.
"Perhaps it's worth hunting for the number 13 in your property search to grab a bargain."