# 121 (عدد)

 ← 120 121 122 →
كميخطأ: الوظيفة "numeral_to_arabic" غير موجودة.
ترتيبي121st
(خطأ: الوظيفة "numeral_to_arabic" غير موجودة.)
التحليل لعوامل112
القواسم1, 11, 121
العدد اليونانيΡΚΑ´
العدد الرومانيCXXI
ثنائي11110012
ثلاثي111113
رباعي13214
خماسي4415
سداسي3216
ثماني1718
اثنا عشريA112
ستة عشري7916
عشريني6120
أساس 363D36

121 (one hundred [and] twenty-one) is the natural number following 120 and preceding 122.

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## في الرياضيات

One hundred [and] twenty-one is

• a square (11 times 11)
• the sum of the powers of 3 from 0 to 4, so a repunit in base 3. Furthermore 121 is the only square of the form ${\displaystyle 1+p+p^{2}+p^{3}+p^{4}}$, where p is prime (3, in this case).[بحاجة لمصدر]
• the sum of three consecutive primes (37 + 41 + 43).
• As 5! + 1 = 121 it is provides a solution to Brocard's problem. There are only two other squares known to be of the form n! + 1, . Another example of 121 being one of the few numbers supporting a conjecture is that Fermat conjectured that 4 and 121 are the only perfect squares of the form x3 - 4 (with x being 2 and 5, respectively).[1]
• It is also a star number and a centered octagonal number.
A Chinese checkers board has 121 holes
• In base 10, it is a Smith number since its digits add up to the same value as its factorization (which uses the same digits) and as a consequence of that it is a Friedman number (11^2). But it can not be expressed as the sum of any other number plus that number's digits, making 121 a self number.

121 هو أيضاً:

## المراجع

1. ^ Wells, D., The Penguin Dictionary of Curious and Interesting Numbers, London: Penguin Group. (1987): 136
2. ^ Vodafone, Calling and messaging
3. ^ Rule 1.1 Archived 2015-01-18 at the Wayback Machine, American Cribbage Congress, retrieved 6 September 2011