666541321 has 8 divisors (see below), whose sum is σ = 706267944. Its totient is φ = 626872320.

The previous prime is 666541313. The next prime is 666541333. The reversal of 666541321 is 123145666.

It can be written as a sum of positive squares in 4 ways, for example, as 325622025 + 340919296 = 18045^2 + 18464^2 .

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 666541321 - 2³ = 666541313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666541301) 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, 10681 + ... + 38041.

It is an arithmetic number, because the mean of its divisors is an integer number (88283493).

Almost surely, 2^666541321 is an apocalyptic number.

It is an amenable number.

666541321 is a deficient number, since it is larger than the sum of its proper divisors (39726623).

666541321 is a wasteful number, since it uses less digits than its factorization.

666541321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28811.

The product of its digits is 25920, while the sum is 34.

The square root of 666541321 is about 25817.4615522131. The cubic root of 666541321 is about 873.5257115417.

Adding to 666541321 its reverse (123145666), we get a palindrome (789686987).

The spelling of 666541321 in words is "six hundred sixty-six million, five hundred forty-one thousand, three hundred twenty-one".