98

Number
$98$ (ninety-eight) is:


 * $2 \times 7^2$


 * With $89$, gives the longest reverse-and-add sequence of any $2$-digit integers, of $24$ terms


 * The $1$st even integer that cannot be expressed as the sum of $2$ prime numbers of which the smaller one is $3$, $5$ or $7$


 * The $1$st 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 even integer after $2$, $4$, $94$, $96$ that cannot be expressed as the sum of $2$ prime numbers which are each one of a pair of twin primes


 * The $5$th after $0$, $2$, $3$, $27$ of the $6$ integers which are the middle term of a sequence of $5$ consecutive integers whose cubes add up to a square
 * $96^3 + 97^3 + 98^3 + 99^3 + 100^3 = 4 \, 708 \, 900 = 2170^2$


 * The $13$th nontotient after $14$, $26$, $34$, $38$, $50$, $62$, $68$, $74$, $76$, $86$, $90$, $94$:
 * $\nexists m \in \Z_{>0}: \map \phi m = 98$
 * where $\map \phi m$ denotes the Euler $\phi$ function


 * The $19$th positive integer $n$ after $5$, $11$, $17$, $23$, $29$, $30$, $36$, $42$, $48$, $54$, $60$, $61$, $67$, $73$, $79$, $85$, $91$, $92$ such that no factorial of an integer can end with $n$ zeroes

Also see

 * 2-Digit Numbers forming Longest Reverse-and-Add Sequence
 * Reciprocal of 98