1720729 has 4 divisors (see below), whose sum is σ = 1762740. Its totient is φ = 1678720.

The previous prime is 1720711. The next prime is 1720769. The reversal of 1720729 is 9270271.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 328329 + 1392400 = 573^2 + 1180^2 .

It is a cyclic number.

It is not a de Polignac number, because 1720729 - 2⁹ = 1720217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1720697 and 1720706.

It is not an unprimeable number, because it can be changed into a prime (1720709) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20944 + ... + 21025.

It is an arithmetic number, because the mean of its divisors is an integer number (440685).

2^1720729 is an apocalyptic number.

It is an amenable number.

1720729 is a deficient number, since it is larger than the sum of its proper divisors (42011).

1720729 is an equidigital number, since it uses as much as digits as its factorization.

1720729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42010.

The product of its (nonzero) digits is 1764, while the sum is 28.

The square root of 1720729 is about 1311.7656040619. The cubic root of 1720729 is about 119.8314531921.

The spelling of 1720729 in words is "one million, seven hundred twenty thousand, seven hundred twenty-nine".