Is there a sign for 'not less than', 'not greater than', etc.?

To answer the question, yes. $$ a \nless b\\ a \ngtr b\\ a \nleq b\qquad a \nleqq b\qquad a \nleqslant b\\ a \ngeq b\qquad a \ngeqq b\qquad a \ngeqslant b $$ and so on for many other mathematical relations $$ a \nleftarrow b\\ a \nLeftarrow b\\ A \nsupseteqq B\\ A \nvdash \phi\qquad A \nVdash \phi\\ \nexists x $$

I would probably use $850 \le 950$, as order is defined for integers.

Equality is special in that there are two ways that two real numbers $a$ and $b$ can be not equal:

$$a>b,b>a$$

So, instead of saying $a>b \;\textrm {or}\;b>a$, we write $b\neq a$.

For the others, each negation has an existing symbol, so:

$$a\not>b \iff a\leq b,\;\,a\nleq b\iff a>b$$

etc.

But like the comments say, either is OK.