665731121 has 8 divisors (see below), whose sum is σ = 745881024. Its totient is φ = 588852720.

The previous prime is 665731109. The next prime is 665731123. The reversal of 665731121 is 121137566.

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 665731121 - 2²² = 661536817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (665731123) 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 7 ways as a sum of consecutive naturals, for example, 817445 + ... + 818258.

It is an arithmetic number, because the mean of its divisors is an integer number (93235128).

Almost surely, 2^665731121 is an apocalyptic number.

It is an amenable number.

665731121 is a deficient number, since it is larger than the sum of its proper divisors (80149903).

665731121 is a wasteful number, since it uses less digits than its factorization.

665731121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1635751.

The product of its digits is 7560, while the sum is 32.

The square root of 665731121 is about 25801.7658504219. The cubic root of 665731121 is about 873.1716362286.

Adding to 665731121 its reverse (121137566), we get a palindrome (786868687).

The spelling of 665731121 in words is "six hundred sixty-five million, seven hundred thirty-one thousand, one hundred twenty-one".