# 43 (number)

 ← 42 43 44 →
Cardinalforty-three
Ordinal43rd
(forty-third)
Factorizationprime
Prime14th
Divisors1, 43
Greek numeralΜΓ´
Roman numeralXLIII
Binary1010112
Ternary11213
Octal538
Duodecimal3712

43 (forty-three) is the natural number following 42 and preceding 44.

## In mathematics

Forty-three is the 14th smallest prime number. The previous is forty-one, with which it comprises a twin prime, and the next is forty-seven. 43 is the smallest prime that is not a Chen prime. It is also the third Wagstaff prime.

43 is the fourth term of Sylvester's sequence, one more than the product of the previous terms (2 × 3 × 7).

43 is a centered heptagonal number.

Let a0 = a1 = 1, and thenceforth an = 1/n − 1(a02 + a12 + ... + an − 12). This sequence continues 1, 1, 2, 3, 5, 10, 28, 154... (sequence A003504 in the OEIS). a43 is the first term of this sequence that is not an integer.

43 is a Heegner number.

43 is the largest prime which divides the order of the Janko group J4.

43 is a repdigit in base 6 (111).

43 is the number of triangles inside the Sri Yantra.

43 is the largest natural number that is not a (original) McNugget number.

43 is the smallest prime number expressible as the sum of 2, 3, 4, or 5 different primes:

• 43 = 41 + 2
• 43 = 11 + 13 + 19
• 43 = 2 + 11 + 13 + 17
• 43 = 3 + 5 + 7 + 11 + 17.

When taking the first six terms of the Taylor series for computing e, one obtains

$\sum _{i=0}^{5}{\frac {1}{i!}}={\frac {163}{60}}=2+{\frac {43}{60}},\$ which is also five minus the fifth harmonic number.

Every solvable configuration of the Fifteen puzzle can be solved in no more than 43 multi-tile moves (i.e. when moving two or three tiles at once is counted as one move).

In auto racing:

## Arts, entertainment, and media

### Popular culture

• Movie 43 (2013) is a film consisting of a series of interconnected short stories, featuring some of the biggest stars in Hollywood, which make up the insane storylines a washed-up producer is pitching to a movie company.
• In The Big Bang Theory episode "The 43 Peculiarity", Howard and Raj try to solve the mystery of Sheldon disappearing every afternoon to a room with a chalkboard that has the number 43 written on it.

Forty-three is: