665891408 has 80 divisors (see below), whose sum is σ = 1639228416. Its totient is φ = 254914560.

The previous prime is 665891393. The next prime is 665891419. The reversal of 665891408 is 804198566.

It is a super-2 number, since 2×665891408² = 886822734496444928, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37760 + ... + 52512.

Almost surely, 2^665891408 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 665891408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (819614208).

665891408 is an abundant number, since it is smaller than the sum of its proper divisors (973337008).

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

665891408 is a wasteful number, since it uses less digits than its factorization.

665891408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14812 (or 14806 counting only the distinct ones).

The product of its (nonzero) digits is 414720, while the sum is 47.

The square root of 665891408 is about 25804.8717880946. The cubic root of 665891408 is about 873.2417079771.

The spelling of 665891408 in words is "six hundred sixty-five million, eight hundred ninety-one thousand, four hundred eight".