99

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Number

$99$ (ninety-nine) is:

$3^2 \times 11$

The $2$nd of the $3$rd pair of consecutive integers which both have $6$ divisors:

$\map {\sigma_0} {98} = \map {\sigma_0} {99} = 6$

The $5$th Kaprekar number after $1$, $9$, $45$, $55$:

$99^2 = 9801 \to 98 + 01 = 99$

The $6$th palindromic lucky number:

$1$, $3$, $7$, $9$, $33$, $99$, $\ldots$

The $8$th integer after $0$, $1$, $3$, $5$, $7$, $9$, $33$ which is palindromic in both decimal and binary:

$99_{10} = 1 \, 100 \, 011_2$

The $12$th trimorphic number after $1$, $4$, $5$, $6$, $9$, $24$, $25$, $49$, $51$, $75$, $76$:

$99^3 = 970 \, 2 \mathbf {99}$

The $22$nd lucky number:

$1$, $3$, $7$, $9$, $13$, $15$, $21$, $25$, $31$, $33$, $37$, $43$, $49$, $51$, $63$, $67$, $73$, $75$, $79$, $87$, $93$, $99$, $\ldots$

Also see

• Previous  ... Next: Sequence of Palindromic Lucky Numbers
• Previous  ... Next: Palindromes in Base 10 and Base 2

• Previous  ... Next: Kaprekar Number

• Previous  ... Next: Trimorphic Number

• Previous  ... Next: Lucky Number

• Previous  ... Next: Pairs of Consecutive Integers with 6 Divisors

Historical Note

The number $99$ is associated with the word amen, used at the end of prayers in the Christian, Judaic and Muslim traditions to denote a strong sense of affirmation: verily or truly with perhaps a sense of let it be made to be so.

The attribution arises from the Greek transliteration $\alpha \mu \eta \nu$, which bear the numerical values $1$, $40$, $8$ and $50$ respectively, totalling $99$.

Hence, in many old editions of the Bible, instead of amen at the end of a prayer, the number $99$ can often be found.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $99$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $99$