729805821 has 4 divisors (see below), whose sum is σ = 973074432. Its totient is φ = 486537212.

The previous prime is 729805807. The next prime is 729805823. The reversal of 729805821 is 128508927.

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: 128508927 = 3 ⋅42836309.

It is a cyclic number.

It is not a de Polignac number, because 729805821 - 2⁶ = 729805757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (729805823) 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, 121634301 + ... + 121634306.

It is an arithmetic number, because the mean of its divisors is an integer number (243268608).

Almost surely, 2^729805821 is an apocalyptic number.

It is an amenable number.

729805821 is a deficient number, since it is larger than the sum of its proper divisors (243268611).

729805821 is a wasteful number, since it uses less digits than its factorization.

729805821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243268610.

The product of its (nonzero) digits is 80640, while the sum is 42.

The square root of 729805821 is about 27014.9184896050. The cubic root of 729805821 is about 900.3314914690.

The spelling of 729805821 in words is "seven hundred twenty-nine million, eight hundred five thousand, eight hundred twenty-one".