FACTBOX-Armenia's presidential election

(Reuters) - Armenians voted on Tuesday in a presidential election that Prime Minister Serzh Sarksyan, given credit for swift economic growth and rising living standards, is expected to win.

Here are some key facts about the vote:

ELECTORATE - The Central Election Commission (CEC) says there are 2.32 million eligible voters out of a population of 3.2 million.

POLLING STATIONS - 1,923 in 41 regions.

VOTING HOURS - Voting opens at 8 a.m. (5 a.m,. British time) on Tuesday and closes at 8 p.m. (5 p.m. British time).

PREVIOUS ELECTION - Armenia held its last presidential election in February 2003. Outgoing leader Robert Kocharyan won in the second round with over 67 percent of the vote. His rival was opposition leader Stepan Demirchyan, who is not running in this election. Kocharyan is not running on Tuesday as he has already served the maximum two consecutive terms.

RULES - A candidate needs 50 percent of all ballots cast plus one vote to win in the first round. If none of the candidates passes that threshold, a second round of voting will take place within two weeks between the two leading candidates.

OBSERVERS - More than 300 foreign observers from the Organisation for Security and Cooperation in Europe (OSCE), as well as dozens from the Council of Europe and other foreign organisations, will monitor voting.

RESULTS - Preliminary results are expected on Wednesday, February 20. Final results must be released within seven days of the vote.