The phrase "a number of underlying" is correct and usable in written English.
It can be used when discussing multiple foundational factors or elements that contribute to a situation or issue.
Example: "There are a number of underlying causes for the recent changes in the market."
Alternatives: "several fundamental" or "multiple core".
Still one feels (perhaps intuits) a number of underlying pulses in this musical personality.
A number of underlying constructs constitute the basis of foresight.
It is now clear that stress and the ageing process share a number of underlying mechanisms bound in a very close, if not indissociable, relationship.
Despite the simplicity of the concept of orthogonal solar cells, there are a number of underlying physical mechanisms which need to be accounted when considering the form factor of orthogonal solar cells.
There are considerable variations in UK and French practice, reflecting a number of underlying factors including attitude to the environment, institutional factors and the nature and perceptions of practitioners.
Artemis Fowl has a number of underlying themes, but the most essential of these are greed and the conflict between good and evil.
However, it has been suggested that, notwithstanding its complexity, cancer could be understood in terms of a small number of underlying principles[ 1].
Because these tests combine subscales that are representative of a broad number of underlying cognitive functions, they are likely to pick up exposure-related deficits across cohorts that differ in their functional expressions of toxicity.
As the prime minister rightly says, the UK economy has a number of fundamental underlying strengths.
The findings challenge a number of assumptions underlying the policies of the Bush administration and private groups that encourage virginity pledges as part of promoting abstinence before marriage.
In fact, there are a number of mechanisms underlying the role immune system plays in tumor cells.
