666997640 has 16 divisors (see below), whose sum is σ = 1500744780. Its totient is φ = 266799040.

The previous prime is 666997577. The next prime is 666997687. The reversal of 666997640 is 46799666.

It can be written as a sum of positive squares in 2 ways, for example, as 592727716 + 74269924 = 24346^2 + 8618^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8337431 + ... + 8337510.

Almost surely, 2^666997640 is an apocalyptic number.

It is an amenable number.

666997640 is an abundant number, since it is smaller than the sum of its proper divisors (833747140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

666997640 is a wasteful number, since it uses less digits than its factorization.

666997640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16674952 (or 16674948 counting only the distinct ones).

The product of its (nonzero) digits is 2939328, while the sum is 53.

The square root of 666997640 is about 25826.2974504670. The cubic root of 666997640 is about 873.7250067383.

The spelling of 666997640 in words is "six hundred sixty-six million, nine hundred ninety-seven thousand, six hundred forty".