For some reason the code below returns a non-zero value. The same problem takes place for any odd number greater than 94906267 and for even numbers looking like 94906267*2+4*N, where N is an any natural number, including zero. I couldn't find any limitations on input value regarding using this function, so it appears to be a malfunctioning.
CAST(STDDEV_POP(val) AS DECIMAL(30,15))
SELECT 94906267 as val
Teradata version - 15.10.07.07d Release - 15.10.07.11