{% if loop.index is divisibleby 3 %}
{#    ^^^^ @variable #}
{#         ^^^^^ @variable.member #}
{#                  ^^^^^^^^^^ @keyword.operator #}

{% if loop.index is divisibleby(3) %}
{#    ^^^^ @variable #}
{#         ^^^^^ @variable.member #}

{% if foo.bar.baz is divisibleby 3 %}
{#    ^^^ @variable #}
{#        ^^^ @variable.member #}
{#            ^^^ @variable.member #}