71

71
Basic Information
Cardinal Number	seventy-one
Ordinal Number	seventy first
Roman Numeral	LXXI
Greek Numeral	ΟΑ´
Factorization	71
Standard Form	7.1 × 101
Different Representations
Binary Form	10001112
Ternary Form	21223
Quaternary Form	10134
Quinary Form	2415
Senary Form	1556
Septenary Form	1317
Octal Form	1078
Nonary Form	789
Undecimal Form	6511
Duodecimal Form	5B12
Tridecimal Form	5613
Quattuordecimal Form	5114
Quindecimal Form	4B15
Hexadecimal Form	4716
Septendecimal Form	4317
Octodecimal Form	3H18
Novemdecimal Form	3E19
Vigesimal Form	3B20
Unvigesimal Form	3821
Duovigesimal Form	3522
Trevigesimal Form	3223
Quattuorvigesimal Form	2N24
Quinvigesimal Form	2L25
Hexavigesimal Form	2J26
Septenvigesimal Form	2H27
Octovigesimal Form	2F28
Novemvigesimal Form	2D29
Trigesimal Form	2B30
Untrigesimal Form	2931
Duotrigesimal Form	2732
Tretrigesimal Form	2533
Quattuortrigesimal Form	2334
Quintrigesimal Form	2135
Hexatrigesimal Form	1Z36
Previous	67
Current	71
Next	73

71 is a prime number from 1-100. 71 has 2 factors, 1 and 71. It is the twentieth prime number, and the twentieth prime number from 1-100.

Proofs

• — 71 is divisible by 1.

• — 71 is not divisible by 2-70.

• — 71 is divisible by 71.

Therefore, 71 has two factors and is prime.

As an Exponent of Mersenne Number

2⁷¹ - 1 can be divided by numbers such as 228,479 and 48,544,121, and is therefore not a prime number.

Relationship with other odd numbers

The numbers before

• 65 is a composite number. Its prime factorization is 5 * 13.
• 67 is the previous prime number.
  • The difference between 71 and 67 is 4. Therefore, they are cousin primes.
• 69, the previous odd number, is a composite number. Its prime factorization is 3 * 23.

The numbers after

• 73 is the next odd number, as well as the next prime number.
  • The difference between 73 and 71 is 2. Therefore, they are twin primes.
• 75 is a composite number. Its prime factorization is 3 * 5².
• 77 is also a composite number. Its prime factorization is 7 * 11.
• 79 is the second next prime number.

Trivia

• 71 is an emirp, since its reverse, 17, is also prime.
  • This also means that, since all permutations of 71 are prime, 71 is a permutable prime.
• 71 is a Pillai prime, since 9! + 1 is divisible by 71, but 71 is not one more than a multiple of 9.
• 71 is a centered heptagonal number.
• 71 is part of the last known pair of Brown numbers along with 7, since 71² = 7! + 1.
• 71 is the 15th and largest supersingular prime.

Prime Numbers 1-1,000