Pull out Account number from result rex?

[showser]

I have this result and  would like to just pull out the accountNumber 12345678

021-05-19_09:36:25.459 ERROR c.r.r.m.m.o.CreateAccountResponseProcessingOrchestratorImpl-c6de96 No Batch ID found in XYZ response. Context:[CommunicationContext{accountKey=AccountKey{accountNumber='12345678', providerCode='BKRBO1'}, correlationId='f1683b92-32ee-4b5e-8b9f-27cb98c6de96', properties={COMMUNICATION_TYPE=CREATE_NEW_ACCOUNT, ENRICH_XYZ_REQUEST=false}}]

[ITWhisperer]

| rex "accountNumber=\'(?<acct>\d+)\'"