665021813 has 8 divisors (see below), whose sum is σ = 673524768. Its totient is φ = 656530704.

The previous prime is 665021809. The next prime is 665021821. The reversal of 665021813 is 318120566.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 665021813 - 2² = 665021809 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 665021813.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665021873) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 181031 + ... + 184667.

It is an arithmetic number, because the mean of its divisors is an integer number (84190596).

Almost surely, 2^665021813 is an apocalyptic number.

It is an amenable number.

665021813 is a deficient number, since it is larger than the sum of its proper divisors (8502955).

665021813 is a wasteful number, since it uses less digits than its factorization.

665021813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5923.

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 665021813 is about 25788.0168489165. The cubic root of 665021813 is about 872.8614170323.

The spelling of 665021813 in words is "six hundred sixty-five million, twenty-one thousand, eight hundred thirteen".