From Wikipedia, the free encyclopedia
Natural number
79 (seventy-nine ) is the
natural number following
78 and preceding
80 .
In mathematics
79 is:
An
odd number.
The smallest number that can not be represented as a sum of fewer than 19
fourth powers .
The 22nd
prime number (between
73 and
83 )
An isolated prime without a
twin prime , as 77 and 81 are composite.
[1]
The smallest prime number p for which the
real quadratic field Q √p ] has
class number greater than 1 (namely 3).
[2]
A
cousin prime with 83.
An
emirp in
base 10 , because the reverse of 79,
97 , is also a prime.
[3]
A
Fortunate prime .
[4]
A
circular prime .
[5]
A prime number that is also a
Gaussian prime (since it is of the form 4n + 3 ).
A
happy prime .
[6]
A
Higgs prime .
[7]
A
lucky prime .
[8]
A
permutable prime , with
ninety-seven .
A
Pillai prime ,
[9] because 23
! + 1 is
divisible by 79, but 79 is not one more than a
multiple of
23 .
A
regular prime .
[10]
A
right-truncatable prime , because when the last digit (9) is removed, the remaining number (7) is still prime.
A
sexy prime (with
73 ).
The n value of the
Wagstaff prime 201487636602438195784363.
Similarly to how the decimal expansion of 1/
89 gives Fibonacci numbers, 1/79 gives
Pell numbers , that is,
1
79
=
∑
n
=
1
∞
P
(
n
)
×
10
−
(
n
+
1
)
=
0.0126582278
…
.
{\displaystyle {\frac {1}{79}}=\sum _{n=1}^{\infty }{P(n)\times 10^{-(n+1)}}=0.0126582278\dots \ .}
A
Leyland number of the second kind .
In science
Signage for table 79 at a restaurant
In astronomy
In other fields
References
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000