1666438 has 4 divisors (see below), whose sum is σ = 2499660. Its totient is φ = 833218.

The previous prime is 1666429. The next prime is 1666447. The reversal of 1666438 is 8346661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 8346661 = 569 ⋅14669.

It is an interprime number because it is at equal distance from previous prime (1666429) and next prime (1666447).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 416608 + ... + 416611.

It is an arithmetic number, because the mean of its divisors is an integer number (624915).

2^1666438 is an apocalyptic number.

1666438 is a deficient number, since it is larger than the sum of its proper divisors (833222).

1666438 is an equidigital number, since it uses as much as digits as its factorization.

1666438 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 833221.

The product of its digits is 20736, while the sum is 34.

The square root of 1666438 is about 1290.9058834787. The cubic root of 1666438 is about 118.5576876154.

The spelling of 1666438 in words is "one million, six hundred sixty-six thousand, four hundred thirty-eight".