Even Numbers and Odd Numbers

A page of the Numeropedia - the Special Encyclopedia of Numbers

All Numbers & [0-9] 0 - 1  - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9  &  [...<0] - [0<...<1]

1  - 10 - 100  - 1000 - 10,000 - 100,000 - 1M - 10M - 100M1B10B - 100B - 1T - 10T - 100T - 1Q - ...

00          None/Never         Number 0         Number 0 in Math.

Odd numbers

[Math.]  An odd number ends with either digit 1, 3, 5, 7 or 9.

[Geology]  In the U.S. interstate highways system

- the odd 1-digit or 2-digit numbers are for north-south routes, increasing to the west.

- the 3-digit numbers with the first digit odd are routes that spur into a city.

Even numbers

[Math.]  An even number ends with either digit 0, 2, 4, 6 or 8. Hence it is divisible by 2.

[Geology] In the U.S. interstate highways system,

- the even 1-digit or 2-digit numbers are for east-west routes, increasing to the south.

- the 3-digit numbers with the first digit even are routes through or around a city.

[Math] Round-up rule: If the decimal part of a number is .5 or higher, round it up to the next whole number, if it is less than .5, round it down to the whole number.

However, banker’s Rounding rule is to round the number with decimal .5 to the nearest even number (not always round it up)

Even vs. Odd

[Math.]  Euler numbers (or secant numbers Ei) are defined by the infinite series: sec(x) = 1/cos(x) = 1+E2(x2/2!)+E4(x4/4!)+E6(x6/6!)+…, where E0 = 1, E2 = –1, E4 = 5, E6 =  –61, E8 = 1,385, E10 = –50,521, E12 = 2,702,765, E14 = –199,360,981, E16 = 19,391,512,145, E18 = –2,404,879,675,441… The odd-indexed Euler numbers are all 0. The even-indexed Euler numbers have alternating signs.

[Trivia]   U.S. Postal Zip Code: Odd, West Virginia 25902.

[Trivia]  Palindrome: "NEVER ODD OR EVEN".

A palndrom is a word, verse, sentence or number that reads the same forward or backward.