6661321 has 4 divisors (see below), whose sum is σ = 6702352. Its totient is φ = 6620292.

The previous prime is 6661313. The next prime is 6661327. The reversal of 6661321 is 1231666.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1231666 = 2 ⋅615833.

It is a cyclic number.

It is not a de Polignac number, because 6661321 - 2³ = 6661313 is a prime.

It is a super-3 number, since 3×6661321³ (a number of 21 digits) contains 333 as substring.

It is a Duffinian number.

6661321 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (6661327) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20271 + ... + 20596.

It is an arithmetic number, because the mean of its divisors is an integer number (1675588).

Almost surely, 2^6661321 is an apocalyptic number.

It is an amenable number.

6661321 is a deficient number, since it is larger than the sum of its proper divisors (41031).

6661321 is a wasteful number, since it uses less digits than its factorization.

6661321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41030.

The product of its digits is 1296, while the sum is 25.

The square root of 6661321 is about 2580.9535059741. The cubic root of 6661321 is about 188.1568876753.

Adding to 6661321 its reverse (1231666), we get a palindrome (7892987).

The spelling of 6661321 in words is "six million, six hundred sixty-one thousand, three hundred twenty-one".