1720720129 has 4 divisors (see below), whose sum is σ = 1720809684. Its totient is φ = 1720630576.

The previous prime is 1720720097. The next prime is 1720720159. The reversal of 1720720129 is 9210270271.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9210270271 = 907 ⋅10154653.

It can be written as a sum of positive squares in 2 ways, for example, as 1033493904 + 687226225 = 32148^2 + 26215^2 .

It is a cyclic number.

It is not a de Polignac number, because 1720720129 - 2⁵ = 1720720097 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1720720129.

It is not an unprimeable number, because it can be changed into a prime (1720720159) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 2902 + ... + 58735.

It is an arithmetic number, because the mean of its divisors is an integer number (430202421).

Almost surely, 2^1720720129 is an apocalyptic number.

It is an amenable number.

1720720129 is a deficient number, since it is larger than the sum of its proper divisors (89555).

1720720129 is an equidigital number, since it uses as much as digits as its factorization.

1720720129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89554.

The product of its (nonzero) digits is 3528, while the sum is 31.

The square root of 1720720129 is about 41481.5637241414. The cubic root of 1720720129 is about 1198.3124726646.

The spelling of 1720720129 in words is "one billion, seven hundred twenty million, seven hundred twenty thousand, one hundred twenty-nine".