665421696 has 128 divisors (see below), whose sum is σ = 2027596800. Its totient is φ = 214617600.

The previous prime is 665421683. The next prime is 665421709. The reversal of 665421696 is 696124566.

665421696 is a `hidden beast` number, since 6 + 6 + 542 + 16 + 96 = 666.

It is an interprime number because it is at equal distance from previous prime (665421683) and next prime (665421709).

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

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, 104031 + ... + 110241.

It is an arithmetic number, because the mean of its divisors is an integer number (15840600).

Almost surely, 2^665421696 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 665421696, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1013798400).

665421696 is an abundant number, since it is smaller than the sum of its proper divisors (1362175104).

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

665421696 is a wasteful number, since it uses less digits than its factorization.

665421696 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6265 (or 6247 counting only the distinct ones).

The product of its digits is 466560, while the sum is 45.

The square root of 665421696 is about 25795.7689553927. The cubic root of 665421696 is about 873.0363348560.

The spelling of 665421696 in words is "six hundred sixty-five million, four hundred twenty-one thousand, six hundred ninety-six".