1721729 has 2 divisors, whose sum is σ = 1721730.
Its totient is φ = 1721728.
The previous prime is 1721719. The next prime is 1721749. The reversal of 1721729 is 9271271.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 1385329 + 336400 = 1177^2 + 580^2
It is a cyclic number.
It is a de Polignac number, because none of the positive numbers 2k-1721729 is a prime.
It is a Chen prime.
It is an Ulam number.
It is not a weakly prime, because it can be changed into another prime (1721719) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860864 + 860865.
It is an arithmetic number, because the mean of its divisors is an integer number (860865).
21721729 is an apocalyptic number.
It is an amenable number.
1721729 is a deficient number, since it is larger than the sum of its proper divisors (1).
1721729 is an equidigital number, since it uses as much as digits as its factorization.
1721729 is an evil number, because the sum of its binary digits is even.
The product of its digits is 1764, while the sum is 29.
The square root of 1721729 is about 1312.1467143578.
The cubic root of 1721729 is about 119.8546620079.
The spelling of 1721729 in words is "one million, seven hundred twenty-one thousand, seven hundred twenty-nine".