The target was reached eight weeks after Mr Aikman's death on 2 February at the age of 31.
Now the Gordon's Fightback campaign is seeking to raise £1m in his memory to fund research into the disease.
Mr Aikman was director of research for the Better Together campaign at the time of his diagnosis.
His campaign has been supported by leading figures in all of Scotland's major political parties.
Gordon's husband Joe Pike said: "I miss Gordon's voice, his eyes and his smile. I miss the in-jokes and affection and finishing each other's sentences.
"But Gordon never wanted pity, and I don't either. I want to turn a negative into a positive. Today, I want everyone to mark Gordon's birthday by giving the gift of a cure for Motor Neurone Disease.
"Gordon's real passion was finding a cure. Doctors do not know what causes Motor Neurone Disease, let alone how to cure it. But scientists in labs doing research provided him with hope. Not that he would be saved, but hope for future generations.
"A cure for MND - that would be a real gift to remember Gordon by."

The London Taxi Company has secured a deal with Ujra Holding Company for 200 black taxis after it initially ordered 200 in assorted colours.
Chinese car maker Geely bought the company, formerly known as LTI, for Â£11.4m in October, when the former owners went into administration.
The United Arab Emirates has also ordered 200 black taxis.
The company said all vehicles are on target for delivery by the end of the year.
On his return from Saudi Arabia, Peter Johansen, vice president of the London Taxi Company, said the cabs are growing in popularity in the Middle East.
He said: "We've got a very good business partner in the Middle East and he's developed the London Taxi concept into Riyadh in particular.
"People prefer to use our taxis over the local taxis because they're more comfortable and, in particular, in Saudi women are treated slightly differently from the westâ€¦
"Because our taxi provides a segregated  compartment, separate from the driver, ladies in Saudi are allowed to use our taxis on their own, whereas they're not allowed to use the local taxis."
The company has also confirmed it is in talks with Azerbaijan which currently owns 1,000 damson-coloured black cabs.
In March, the London Taxi Company said it would take on about 100 staff, in addition to its 107 workers, to restart production at the Coventry factory on Holyhead Road.
About 156 people lost their jobs when former owners Manganese Bronze Holdings went into administration.
The fund named after Scottish motor neurone disease (MND) campaigner Gordon Aikman has raised £600,000.
[NEXT_CONCEPT]
A Coventry-based black taxi manufacturer is to sell 400 cabs to Saudi Arabia.