666638 has 16 divisors (see below), whose sum is σ = 1210464. Its totient is φ = 268800.

The previous prime is 666637. The next prime is 666643. The reversal of 666638 is 836666.

It is a junction number, because it is equal to n+sod(n) for n = 666598 and 666607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666637) 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, 1163 + ... + 1638.

It is an arithmetic number, because the mean of its divisors is an integer number (75654).

2⁶⁶⁶⁶³⁸ is an apocalyptic number.

666638 is a deficient number, since it is larger than the sum of its proper divisors (543826).

666638 is a wasteful number, since it uses less digits than its factorization.

666638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2827.

The product of its digits is 31104, while the sum is 35.

The square root of 666638 is about 816.4790260625. The cubic root of 666638 is about 87.3567943237.

The spelling of 666638 in words is "six hundred sixty-six thousand, six hundred thirty-eight".