666289981 has 4 divisors (see below), whose sum is σ = 761474272. Its totient is φ = 571105692.

The previous prime is 666289979. The next prime is 666289997. The reversal of 666289981 is 189982666.

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.

It is a cyclic number.

It is not a de Polignac number, because 666289981 - 2¹ = 666289979 is a prime.

It is a super-2 number, since 2×666289981² = 887884677561960722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666289901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47592135 + ... + 47592148.

It is an arithmetic number, because the mean of its divisors is an integer number (190368568).

Almost surely, 2^666289981 is an apocalyptic number.

It is an amenable number.

666289981 is a deficient number, since it is larger than the sum of its proper divisors (95184291).

666289981 is an equidigital number, since it uses as much as digits as its factorization.

666289981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95184290.

The product of its digits is 2239488, while the sum is 55.

The square root of 666289981 is about 25812.5934574579. The cubic root of 666289981 is about 873.4159011182.

The spelling of 666289981 in words is "six hundred sixty-six million, two hundred eighty-nine thousand, nine hundred eighty-one".