1661
1661 is the year the first European banknotes were issued.
- Odd
- Composite
Where 1661 fits
Why 1661 is special
Stockholms Banco issued notes to replace copper plate money so heavy it required a cart. The bank over-issued and collapsed within decades, which is also the first lesson in paper currency.
Same number, different meanings
How 1661 is understood across different contexts — never implying one meaning because of another.
- Mathematics
Stockholms Banco issued notes to replace copper plate money so heavy it required a cart. The bank over-issued and collapsed within decades, which is also the first lesson in paper currency.
- History
In 1661, Robert Boyle's The Sceptical Chymist argued for chemistry as an experimental science distinct from alchemy (England).
- Finance & economics
Sweden's Stockholms Banco issued Europe's first banknotes in 1661 to replace copper plates weighing many kilograms. It then issued more than it could redeem and failed, establishing both the instrument and its characteristic risk.
1661 is part of
Factors & digit properties
- Divisors (4)
- 1, 11, 151, 1661
- Prime factorisation
- 11 × 151
- Digit sum
- 14
- Digital root
- 5
Representations
- Decimal
- 1661
- Scientific notation
- 1.661 × 10^3
Roman numerals
M D C L X I
Binary
1 1 0 0 1 1 1 1 1 0 1
1 × 1,024 + 1 × 512 + 0 × 256 + 0 × 128 + 1 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 1,661
Octal
3 1 7 5
3 × 512 + 1 × 64 + 7 × 8 + 5 × 1 = 1,661
Hexadecimal
6 7 d
6 × 256 + 7 × 16 + d × 1 = 1,661
Read as powers of two: 1,024 + 512 + 64 + 32 + 16 + 8 + 4 + 1 = 1,661.
In historical numeral systems
Egyptian
1 lotus, 6 coils of rope, 6 hobbles, 1 stroke
1 × 1,000 + 6 × 100 + 6 × 10 + 1 × 1 = 1,661. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 corner wedges + 7 vertical wedges (sixties place), 4 corner wedges + 1 vertical wedge (units place)
27 × 60 + 41 = 1661. Places are separated by a space on the tablet, with the higher place written first.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Palindromic number
- Deficient number
- Semiprime
Related numbers & connections
1661 is a year in the 17th century, in the 1660s.
Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
History
In 1661, Robert Boyle's The Sceptical Chymist argued for chemistry as an experimental science distinct from alchemy (England).
DocumentedHistoryGeography: EnglandPeriod: 1661
Finance & economics
Sweden's Stockholms Banco issued Europe's first banknotes in 1661 to replace copper plates weighing many kilograms. It then issued more than it could redeem and failed, establishing both the instrument and its characteristic risk.
DocumentedFinance & economicsGeography: SwedenPeriod: 1661
Common questions
Is 1661 a prime number?
No, 1661 is not prime.
What are the factors of 1661?
The factors of 1661 are 1, 11, 151, 1661.
What is 1661 in Roman numerals?
1661 in Roman numerals is MDCLXI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026