It is a tau number, because it is divible by the number of its divisors (128).
It is an unprimeable number.
Almost surely, 21261637912704 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 1261637912704, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1405944368640).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
1261637912704 is a wasteful number, since it uses less digits than its factorization.
1261637912704 is an evil number, because the sum of its binary digits is even.
The spelling of 1261637912704 in words is "one trillion, two hundred sixty-one billion, six hundred thirty-seven million, nine hundred twelve thousand, seven hundred four".