6665861 has 2 divisors, whose sum is σ = 6665862. Its totient is φ = 6665860.

The previous prime is 6665843. The next prime is 6665873. The reversal of 6665861 is 1685666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3876961 + 2788900 = 1969^2 + 1670^2 .

It is a cyclic number.

It is not a de Polignac number, because 6665861 - 2⁶ = 6665797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6665801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3332930 + 3332931.

It is an arithmetic number, because the mean of its divisors is an integer number (3332931).

Almost surely, 2^6665861 is an apocalyptic number.

It is an amenable number.

6665861 is a deficient number, since it is larger than the sum of its proper divisors (1).

6665861 is an equidigital number, since it uses as much as digits as its factorization.

6665861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 51840, while the sum is 38.

The square root of 6665861 is about 2581.8328760785. The cubic root of 6665861 is about 188.1996238572.

It can be divided in two parts, 66 and 65861, that multiplied together give a triangular number (4346826 = T₂₉₄₈).

The spelling of 6665861 in words is "six million, six hundred sixty-five thousand, eight hundred sixty-one".