665905280 has 128 divisors (see below), whose sum is σ = 1665362160. Its totient is φ = 254361600.

The previous prime is 665905277. The next prime is 665905301. The reversal of 665905280 is 82509566.

It can be written as a sum of positive squares in 8 ways, for example, as 180848704 + 485056576 = 13448^2 + 22024^2 .

It is a tau number, because it is divible by the number of its divisors (128).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1444250 + ... + 1444710.

Almost surely, 2^665905280 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 665905280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (832681080).

665905280 is an abundant number, since it is smaller than the sum of its proper divisors (999456880).

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

665905280 is a wasteful number, since it uses less digits than its factorization.

665905280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 578 (or 566 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 41.

The square root of 665905280 is about 25805.1405731494. The cubic root of 665905280 is about 873.2477717911.

The spelling of 665905280 in words is "six hundred sixty-five million, nine hundred five thousand, two hundred eighty".