1728190921 has 2 divisors, whose sum is σ = 1728190922. Its totient is φ = 1728190920.

The previous prime is 1728190909. The next prime is 1728190943. The reversal of 1728190921 is 1290918271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1727649225 + 541696 = 41565^2 + 736^2 .

It is a cyclic number.

It is not a de Polignac number, because 1728190921 - 2¹⁷ = 1728059849 is a prime.

It is not a weakly prime, because it can be changed into another prime (1728190421) 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 as a sum of consecutive naturals, namely, 864095460 + 864095461.

It is an arithmetic number, because the mean of its divisors is an integer number (864095461).

Almost surely, 2^1728190921 is an apocalyptic number.

It is an amenable number.

1728190921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1728190921 is an equidigital number, since it uses as much as digits as its factorization.

1728190921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18144, while the sum is 40.

The square root of 1728190921 is about 41571.5157409494. The cubic root of 1728190921 is about 1200.0441930484.

The spelling of 1728190921 in words is "one billion, seven hundred twenty-eight million, one hundred ninety thousand, nine hundred twenty-one".