One possible solution:
plot(rand(100,1).*1e6) set(gca, 'YTickLabel', num2str(get(gca,'YTick')','%d'))
Obviously, you can customize the formatting to your liking.

Another example for x-axis ticks. In this case, the labels will overlap with each other. One possible solution is to use the XTICKLABEL_ROTATE function from file Exchange.
plot(5.77*1e6:5.77*1e6+9, rand(1,10)) set(gca, 'XTickLabel', num2str(get(gca,'XTick')','%d')) %#' xticklabel_rotate([],45) %

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