729809721 has 6 divisors (see below), whose sum is σ = 1054169610. Its totient is φ = 486539808.

The previous prime is 729809687. The next prime is 729809789. The reversal of 729809721 is 127908927.

It can be written as a sum of positive squares in only one way, i.e., 606932496 + 122877225 = 24636^2 + 11085^2 .

It is not a de Polignac number, because 729809721 - 2¹³ = 729801529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (729809791) 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 5 ways as a sum of consecutive naturals, for example, 40544976 + ... + 40544993.

It is an arithmetic number, because the mean of its divisors is an integer number (175694935).

Almost surely, 2^729809721 is an apocalyptic number.

It is an amenable number.

729809721 is a deficient number, since it is larger than the sum of its proper divisors (324359889).

729809721 is a wasteful number, since it uses less digits than its factorization.

729809721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81089975 (or 81089972 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 45.

The square root of 729809721 is about 27014.9906718474. The cubic root of 729809721 is about 900.3330952228. Note that the first 3 decimals are identical.

The spelling of 729809721 in words is "seven hundred twenty-nine million, eight hundred nine thousand, seven hundred twenty-one".