• 79 can be written using four 4's:

79 has 2 divisors, whose sum is σ = 80. Its totient is φ = 78.

The previous prime is 73. The next prime is 83. The reversal of 79 is 97.

It is a happy number.

79 is an esthetic number in base 9, base 12 and base 15, because in such bases its adjacent digits differ by 1.

It is a strong prime.

79 is a truncatable prime.

It is an emirp because it is prime and its reverse (97) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 79 - 2^{3} = 71 is a prime.

It is a pancake number, because a pancake can be divided into 79 parts by 12 straight cuts.

It is a Kynea number, being equal to (2^{3} + 1)^{2} - 2.

79 is a modest number, since divided by 9 gives 7 as remainder.

79 is a lucky number.

It is a plaindrome in base 8, base 10, base 12, base 14 and base 16.

It is a nialpdrome in base 3, base 6, base 9, base 11, base 13 and base 15.

It is a congruent number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39 + 40.

It is an arithmetic number, because the mean of its divisors is an integer number (40).

79 is a deficient number, since it is larger than the sum of its proper divisors (1).

79 is an equidigital number, since it uses as much as digits as its factorization.

79 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 63, while the sum is 16.

The square root of 79 is about 8.8881944173. Note that the first 3 decimals coincide. The cubic root of 79 is about 4.2908404270.

Subtracting from 79 its product of digits (63), we obtain a 4-th power (16 = 2^{4}).

The spelling of 79 in words is "seventy-nine", and thus it is an aban number, an oban number, and an uban number.

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