1666729 has 2 divisors, whose sum is σ = 1666730. Its totient is φ = 1666728.

The previous prime is 1666727. The next prime is 1666733. The reversal of 1666729 is 9276661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1567504 + 99225 = 1252^2 + 315^2 .

It is a cyclic number.

It is not a de Polignac number, because 1666729 - 2¹ = 1666727 is a prime.

Together with 1666727, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1666727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833364 + 833365.

It is an arithmetic number, because the mean of its divisors is an integer number (833365).

2^1666729 is an apocalyptic number.

It is an amenable number.

1666729 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666729 is an equidigital number, since it uses as much as digits as its factorization.

1666729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 37.

The square root of 1666729 is about 1291.0185901063. The cubic root of 1666729 is about 118.5645882180.

The spelling of 1666729 in words is "one million, six hundred sixty-six thousand, seven hundred twenty-nine".