728509891 has 4 divisors (see below), whose sum is σ = 771363432. Its totient is φ = 685656352.

The previous prime is 728509883. The next prime is 728509907. The reversal of 728509891 is 198905827.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198905827 = 31 ⋅6416317.

It is a cyclic number.

It is not a de Polignac number, because 728509891 - 2³ = 728509883 is a prime.

It is a super-2 number, since 2×728509891² = 1061453322569663762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (728509861) 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, 21426745 + ... + 21426778.

It is an arithmetic number, because the mean of its divisors is an integer number (192840858).

Almost surely, 2^728509891 is an apocalyptic number.

728509891 is a deficient number, since it is larger than the sum of its proper divisors (42853541).

728509891 is a wasteful number, since it uses less digits than its factorization.

728509891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42853540.

The product of its (nonzero) digits is 362880, while the sum is 49.

The square root of 728509891 is about 26990.9223814230. The cubic root of 728509891 is about 899.7982638375.

The spelling of 728509891 in words is "seven hundred twenty-eight million, five hundred nine thousand, eight hundred ninety-one".