6660781 has 2 divisors, whose sum is σ = 6660782. Its totient is φ = 6660780.

The previous prime is 6660763. The next prime is 6660791. The reversal of 6660781 is 1870666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6375625 + 285156 = 2525^2 + 534^2 .

It is a cyclic number.

It is not a de Polignac number, because 6660781 - 2¹⁷ = 6529709 is a prime.

It is a super-2 number, since 2×6660781² = 88732007059922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6660721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3330390 + 3330391.

It is an arithmetic number, because the mean of its divisors is an integer number (3330391).

Almost surely, 2^6660781 is an apocalyptic number.

It is an amenable number.

6660781 is a deficient number, since it is larger than the sum of its proper divisors (1).

6660781 is an equidigital number, since it uses as much as digits as its factorization.

6660781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 6660781 is about 2580.8488913534. The cubic root of 6660781 is about 188.1518032251.

The spelling of 6660781 in words is "six million, six hundred sixty thousand, seven hundred eighty-one".