It has 4 syllables. If you have questions about the syllables of any other word, check a dictionary, they will always have the syllables. 
According to the Oxford American Dictionary (published by Avon in 1980), there are 4 syllables in the word "necessary."The dictionary breaks the word up into the following syllables this way:nec es sar y
There are four syllables: dict-shun-air-ee.
Random House Online Dictionary and Thorndyke-Barnhart World Book Dictionary show magnolia having 3 syllables: mag-no-lia. It can be pronounced with either 3 syllables (mag-nohl-yuh) or 4 syllables (mag-no-lee-uh), with 3 syllables as first choice.
Two: fe-ver. One way to determine how many syllables a word has, as well as where to divide the word into its syllables, is to look it up in a dictionary.
African has three syllables. http://www.merriam-webster.com/dictionary/african
The dictionary notates correct pronunciation of "any", as an-y; 2 syllables.
3 dic-tio-nary
Well, if you look in the dictionary it separates them as: ex·haust  or [ig-zawst.]
According to a dictionary, the word critique is pronounced kri-teek and so has two syllables (cri-tique).
Four (ed-u-ca-tion).Macmillan Dictionary for Children. Childcraft Dictionary. World Books, Inc. 1975. Print.Four (ed-u-ca-tion).Macmillan Dictionary for Children. Childcraft Dictionary. World Books, Inc. 1975. Print.
This information can be found in a dictionary. Dictionaries provide the pronunciation of words, including the number of syllables in each word. Thesauruses do not typically include syllable count information.