The vibrations of the number 13 are very, very powerful.
Such power can be recognized and embraced and utilized for the benefit of self and others. The power can also be frightening and considered something to be avoided or taboo. So says this article at affinityseries.com
The power inherent in the number 13 is neither "good" nor "bad". Power is just energy until utilized.
Its power is one of the reasons for it’s negative reputation. Those who do not resonate with its vibrations find the vibes to be an obstacle and will certainly experience negative circumstances in their lives.
13 represents the basic triad, 1-2-3 as self-partnership-group. The individual digits in the number 13 add up to the number 4, which represents building a foundation for the future.
The number 13 has the foundational vibration of humanity.
Resonating with the vibrations of the number 13 can result in profound understandings. The knowledge can be used for good or for evil, as past masters of the knowledge have demonstrated — the wizards and witches and magicians of lore.
The use of that understanding to gain what was unwanted by others or to gain control over others may be another reason for the number’s negative reputation.
Everything is balanced. When something can be used for good, it can also be used for bad.
With a number as powerful as 13, the effects can be dramatic and profound and can have a long-lasting ripple effect into the future.