729721 has 4 divisors (see below), whose sum is σ = 761472. Its totient is φ = 697972.

The previous prime is 729719. The next prime is 729737. The reversal of 729721 is 127927.

It is a happy number.

729721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127927 = 19 ⋅6733.

It is a cyclic number.

It is not a de Polignac number, because 729721 - 2¹ = 729719 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 729721.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (729761) 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, 15841 + ... + 15886.

It is an arithmetic number, because the mean of its divisors is an integer number (190368).

2⁷²⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

729721 is a deficient number, since it is larger than the sum of its proper divisors (31751).

729721 is a wasteful number, since it uses less digits than its factorization.

729721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31750.

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

The square root of 729721 is about 854.2370865281. The cubic root of 729721 is about 90.0296610055.

The spelling of 729721 in words is "seven hundred twenty-nine thousand, seven hundred twenty-one".