665055121 has 4 divisors (see below), whose sum is σ = 686508544. Its totient is φ = 643601700.

The previous prime is 665055103. The next prime is 665055133. The reversal of 665055121 is 121550566.

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 665055121 - 2⁵ = 665055089 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 21453391 = 665055121 / (6 + 6 + 5 + 0 + 5 + 5 + 1 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665055421) 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, 10726665 + ... + 10726726.

It is an arithmetic number, because the mean of its divisors is an integer number (171627136).

Almost surely, 2^665055121 is an apocalyptic number.

It is an amenable number.

665055121 is a deficient number, since it is larger than the sum of its proper divisors (21453423).

665055121 is a wasteful number, since it uses less digits than its factorization.

665055121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21453422.

The product of its (nonzero) digits is 9000, while the sum is 31.

The square root of 665055121 is about 25788.6626446584. The cubic root of 665055121 is about 872.8759893777.

The spelling of 665055121 in words is "six hundred sixty-five million, fifty-five thousand, one hundred twenty-one".