42

is the integer between.

Math features
$$\frac{1}{2}+\frac{1}{3}+\frac{1}{7}+\frac{1}{42} = 1$$.
 * 42 is an even number.
 * 42 is a Harshad number and a composite number.
 * 42 is a pronic number and an abundant number.
 * Being a primary pseudoperfect number,
 * 42 is a pentadecagonal (15-gonal) number.
 * 42 has 3 distinct prime factors, making 42 a sphenic number with an abundance of 12.