1265561664 has 56 divisors (see below), whose sum is σ = 3359322720. Its totient is φ = 420486144.

The previous prime is 1265561641. The next prime is 1265561677. The reversal of 1265561664 is 4661655621.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49567 + ... + 70625.

Almost surely, 2^1265561664 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 1265561664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1679661360).

1265561664 is an abundant number, since it is smaller than the sum of its proper divisors (2093761056).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1265561664 is a wasteful number, since it uses less digits than its factorization.

1265561664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21387 (or 21377 counting only the distinct ones).

The product of its digits is 259200, while the sum is 42.

The square root of 1265561664 is about 35574.7335056779. The cubic root of 1265561664 is about 1081.6691337123.

The spelling of 1265561664 in words is "one billion, two hundred sixty-five million, five hundred sixty-one thousand, six hundred sixty-four".