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61 (sixty-one) is a positive integer following 60 and preceding 62. Its ordinal form is written "sixty-first" or 61st.

Properties Edit

61 is an odd prime number.

61 is the 9th Mersenne exponent.

In googology Edit

In Greek-based number-naming systems, 61 is associated with prefix "henhexaconta-", and with prefix "unsexaginti-" in Latin systems.

It is one of the values of the weak Goodstein function: \(g(5)=61\).

It is equal to gag-three with the gag prefix, since A(3,3) in the Ackermann function equals 61.

In science Edit

There are 61 particles in the Standard Model.

It is also the atomic number of the chemical element promethium, the first one having no isotopes with a half-life longer than that of humans.