• 71 can be written using four 4's:

71 has 2 divisors, whose sum is σ = 72. Its totient is φ = 70.

The previous prime is 67. The next prime is 73. The reversal of 71 is 17.

71 is nontrivially palindromic in base 7.

71 is an esthetic number in base 9, base 11 and base 13, because in such bases its adjacent digits differ by 1.

It is a strong prime.

71 is a truncatable prime.

It is an emirp because it is prime and its reverse (17) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 71 - 2^{2} = 67 is a prime.

Together with 73, it forms a pair of twin primes.

It is a Chen prime.

71 is an undulating number in base 7.

It is a plaindrome in base 6, base 9, base 12, base 13, base 15 and base 16.

It is a nialpdrome in base 10, base 11 and base 14.

It is a congruent number.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35 + 36.

It is an arithmetic number, because the mean of its divisors is an integer number (36).

71 is the 5-th centered heptagonal number.

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

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

71 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7, while the sum is 8.

The square root of 71 is about 8.4261497732. The cubic root of 71 is about 4.1408177494.

Adding to 71 its reverse (17), we get a palindrome (88).

The spelling of 71 in words is "seventy-one", and thus it is an aban number, an iban number, and an uban number.

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