The number 81

Representation numerals

Greek numeral

παʹ

Arabic numeral

٨١

Roman numeral

LXXXI

Maya numeral

●●●●
●

Chinese numeral

八十一

Hebrew numeral

פא
Numeral systems
Binary: 1010001
Septimal (base 7): 144
Octal: 121
Hexadecimal: 51
Base 24: 39
Factorization
81 = 3 × 3 × 3 × 3
81 has 5 divisors: 1, 3, 9, 27, 81
Sum of all divisors other than 81: 40
81 = 9 2
81 = 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17
81 = 3 4
Sums & differences
Difference of 2 squares: 81 = 152 - 122 = 412 - 402
Characteristics
81 is a heptagonal number
Related primes
The 81th prime number is: 419
Previous prime number: 79 — Next prime number: 83

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