I have a lightning datatable with column as type number
The row value in it is getting right aligned, while everything else is left aligned, I need to make it uniform. 
Here is what I tried --
<div class="empFamilyTable"> <lightning:datatable aura:id="accountTable" keyField="Id" hideCheckboxColumn="true" columns="{!v.FamilyDetailColumns}" data="{!v.FamilyDetailData}" onrowaction="{! c.handleRowAction }"/> </div> CSS--
.THIS .empFamilyTable td { text-align: left !important; } Number data types cell are aligned with css class slds-grid_align-end. It basically used to grow from the end of the horizontal axis. so if you override below style for slds-grid_align-end class then it will left align all number fields.
.THIS .slds-grid_align-end { justify-content: left !important; } Refer SLDS guide for this.
In the attribute FamilyDetailColumns , try to use cellAttributes and apply alignment for the number column like this:
var columns = [{ label: 'Amount', fieldName: 'amount', type: 'currency', cellAttributes: { alignment: 'left' }} // other column data ]; For more details refer to documentation below in section Aligning Data in a Column https://developer.salesforce.com/docs/component-library/bundle/lightning-datatable/documentation
use slds-align_absolute-center
const columns = [ { label: 'Action', type: 'button', typeAttributes: { label: 'Try me' }, cellAttributes: { class: 'slds-align_absolute-center' // Center the button within the cell } } ]; 