1668729 has 4 divisors (see below), whose sum is σ = 2224976. Its totient is φ = 1112484.

The previous prime is 1668727. The next prime is 1668739. The reversal of 1668729 is 9278661.

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 not a de Polignac number, because 1668729 - 2¹ = 1668727 is a prime.

It is a D-number.

It is a Duffinian number.

1668729 is a lucky number.

It is a nialpdrome in base 6.

It is not an unprimeable number, because it can be changed into a prime (1668721) by changing a digit.

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, 278119 + ... + 278124.

It is an arithmetic number, because the mean of its divisors is an integer number (556244).

2^1668729 is an apocalyptic number.

It is an amenable number.

1668729 is a deficient number, since it is larger than the sum of its proper divisors (556247).

1668729 is an equidigital number, since it uses as much as digits as its factorization.

1668729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556246.

The product of its digits is 36288, while the sum is 39.

The square root of 1668729 is about 1291.7929400643. The cubic root of 1668729 is about 118.6119933234.

The spelling of 1668729 in words is "one million, six hundred sixty-eight thousand, seven hundred twenty-nine".