667986661 has 8 divisors (see below), whose sum is σ = 718875864. Its totient is φ = 618385920.

The previous prime is 667986653. The next prime is 667986707. The reversal of 667986661 is 166689766.

It can be written as a sum of positive squares in 4 ways, for example, as 14212900 + 653773761 = 3770^2 + 25569^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 667986661 - 2³ = 667986653 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 (667986611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 321040 + ... + 323113.

It is an arithmetic number, because the mean of its divisors is an integer number (89859483).

Almost surely, 2^667986661 is an apocalyptic number.

667986661 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

667986661 is a deficient number, since it is larger than the sum of its proper divisors (50889203).

667986661 is a wasteful number, since it uses less digits than its factorization.

667986661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 644231.

The product of its digits is 3919104, while the sum is 55.

The square root of 667986661 is about 25845.4379146495. The cubic root of 667986661 is about 874.1566452575.

The spelling of 667986661 in words is "six hundred sixty-seven million, nine hundred eighty-six thousand, six hundred sixty-one".