It is a happy number.
It is an unprimeable number.
21561356 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 1561356, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2100560).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
1561356 is a wasteful number, since it uses less digits than its factorization.
1561356 is an odious number, because the sum of its binary digits is odd.
The square root of 1561356 is about 1249.5423162102. The cubic root of 1561356 is about 116.0113940453.
The spelling of 1561356 in words is "one million, five hundred sixty-one thousand, three hundred fifty-six".