665390121 has 16 divisors (see below), whose sum is σ = 977427648. Its totient is φ = 399272000.

The previous prime is 665390083. The next prime is 665390137. The reversal of 665390121 is 121093566.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 665390121 - 2⁶ = 665390057 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (665390171) by changing a digit.

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, 96486 + ... + 103151.

It is an arithmetic number, because the mean of its divisors is an integer number (61089228).

Almost surely, 2^665390121 is an apocalyptic number.

It is an amenable number.

665390121 is a deficient number, since it is larger than the sum of its proper divisors (312037527).

665390121 is a wasteful number, since it uses less digits than its factorization.

665390121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199752.

The product of its (nonzero) digits is 9720, while the sum is 33.

The square root of 665390121 is about 25795.1569291602. The cubic root of 665390121 is about 873.0225257890.

The spelling of 665390121 in words is "six hundred sixty-five million, three hundred ninety thousand, one hundred twenty-one".