I'm so sorry for you loss.
Answer, no, this is not a Required Minimum Distribution (RMD) for you.
RMD's would have pertained to your father, when he was filing his income tax return. The IRS requires people who have retirement funds to take RMD's when they reach the age of 70½ on the date that is 6 calendar months after their 70th birthday.
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If your mother was age 70 1/2 or older then the IRA distribution is a RMD. Just answer yes it was all a RMD since you closed the account.
Beneficiaries of IRA'a are require to take the RMD if the owner of the account was, however determining the RMD amount is not necessary unless less than the RMD was taken. Closing the account guarantees that the RMD was satisfied.