Number of testimonies
( Number ( of testimonies ) )
(ROOT (NP (NP (NNP Number)) (PP (IN of) (NP (NNS testimonies)))))
There are a number of testimonials. 
( There ( ( are ( ( a number ) ( of testimonials ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (DT a) (NN number)) (PP (IN of) (NP (NNS testimonials))))) (. .)))