It is a congruent number.
It is an unprimeable number.
21999980 is an apocalyptic number.
1999980 is a gapful number since it is divisible by the number (10) formed by its first and last digit.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 1999980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3118752).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
1999980 is a wasteful number, since it uses less digits than its factorization.
1999980 is an evil number, because the sum of its binary digits is even.
The square root of 1999980 is about 1414.2064912876. The cubic root of 1999980 is about 125.9916850144.
1999980 divided by its sum of digits (45) gives a palindrome (44444).
The spelling of 1999980 in words is "one million, nine hundred ninety-nine thousand, nine hundred eighty".