665562021 has 4 divisors (see below), whose sum is σ = 887416032. Its totient is φ = 443708012.

The previous prime is 665562011. The next prime is 665562043. The reversal of 665562021 is 120265566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 665562021 - 2⁵ = 665561989 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665562011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110927001 + ... + 110927006.

It is an arithmetic number, because the mean of its divisors is an integer number (221854008).

Almost surely, 2^665562021 is an apocalyptic number.

It is an amenable number.

665562021 is a deficient number, since it is larger than the sum of its proper divisors (221854011).

665562021 is a wasteful number, since it uses less digits than its factorization.

665562021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221854010.

The product of its (nonzero) digits is 21600, while the sum is 33.

The square root of 665562021 is about 25798.4887348077. The cubic root of 665562021 is about 873.0976995584.

The spelling of 665562021 in words is "six hundred sixty-five million, five hundred sixty-two thousand, twenty-one".