My Alexa does not care if the number is "24" or "twenty four" as long as it is sent a string. try something like this
a number is injected, the change node concatenates it in the reply string converting the number to a string at same time.
e.g.
[{"id":"c04df06e9a03e5dc","type":"inject","z":"c791cbc0.84f648","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"20","payloadType":"num","x":230,"y":1760,"wires":[["bab69827.23e41"]]},{"id":"bab69827.23e41","type":"change","z":"c791cbc0.84f648","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"\"the temperature is \" & $$.payload & \" degrees celcius\"","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":360,"y":1700,"wires":[["d8b275f2b92b9d8d"]]},{"id":"d8b275f2b92b9d8d","type":"alexa-remote-routine","z":"c791cbc0.84f648","name":"","account":"c8738129.d902c","routineNode":{"type":"speak","payload":{"type":"regular","text":{"type":"msg","value":"payload"},"devices":["G090LF1182850C6D"]}},"x":570,"y":1760,"wires":[[]]},{"id":"c8738129.d902c","type":"alexa-remote-account","name":"alexa remote 2","authMethod":"proxy","proxyOwnIp":"localhost","proxyPort":"3456","cookieFile":"","refreshInterval":"14","alexaServiceHost":"layla.amazon.co.uk","amazonPage":"amazon.co.uk","acceptLanguage":"en-GB","userAgent":"","useWsMqtt":"on","autoInit":"off"}]
