6661543 has 4 divisors (see below), whose sum is σ = 7613200. Its totient is φ = 5709888.

The previous prime is 6661511. The next prime is 6661547. The reversal of 6661543 is 3451666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3451666 = 2 ⋅1725833.

It is a cyclic number.

It is not a de Polignac number, because 6661543 - 2⁵ = 6661511 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6661547) 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 3 ways as a sum of consecutive naturals, for example, 475818 + ... + 475831.

It is an arithmetic number, because the mean of its divisors is an integer number (1903300).

Almost surely, 2^6661543 is an apocalyptic number.

6661543 is a deficient number, since it is larger than the sum of its proper divisors (951657).

6661543 is an equidigital number, since it uses as much as digits as its factorization.

6661543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 951656.

The product of its digits is 12960, while the sum is 31.

The square root of 6661543 is about 2580.9965129771. The cubic root of 6661543 is about 188.1589778696.

It can be divided in two parts, 666 and 1543, that added together give a square (2209 = 47²).

The spelling of 6661543 in words is "six million, six hundred sixty-one thousand, five hundred forty-three".