6661744861 has 4 divisors (see below), whose sum is σ = 6668855452. Its totient is φ = 6654634272.

The previous prime is 6661744841. The next prime is 6661744877. The reversal of 6661744861 is 1684471666.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3718682361 + 2943062500 = 60981^2 + 54250^2 .

It is a cyclic number.

It is not a de Polignac number, because 6661744861 - 2¹⁷ = 6661613789 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6661744841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3553890 + ... + 3555763.

It is an arithmetic number, because the mean of its divisors is an integer number (1667213863).

Almost surely, 2^6661744861 is an apocalyptic number.

It is an amenable number.

6661744861 is a deficient number, since it is larger than the sum of its proper divisors (7110591).

6661744861 is an equidigital number, since it uses as much as digits as its factorization.

6661744861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7110590.

The product of its digits is 1161216, while the sum is 49.

The square root of 6661744861 is about 81619.5127466466. The cubic root of 6661744861 is about 1881.6087840902.

The spelling of 6661744861 in words is "six billion, six hundred sixty-one million, seven hundred forty-four thousand, eight hundred sixty-one".