728811661 has 4 divisors (see below), whose sum is σ = 731583072. Its totient is φ = 726040252.

The previous prime is 728811647. The next prime is 728811667. The reversal of 728811661 is 166118827.

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.

It is a cyclic number.

It is not a de Polignac number, because 728811661 - 2¹⁵ = 728778893 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (728811667) 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, 1385311 + ... + 1385836.

It is an arithmetic number, because the mean of its divisors is an integer number (182895768).

Almost surely, 2^728811661 is an apocalyptic number.

It is an amenable number.

728811661 is a deficient number, since it is larger than the sum of its proper divisors (2771411).

728811661 is a wasteful number, since it uses less digits than its factorization.

728811661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2771410.

The product of its digits is 32256, while the sum is 40.

The square root of 728811661 is about 26996.5120154438. The cubic root of 728811661 is about 899.9224875631.

The spelling of 728811661 in words is "seven hundred twenty-eight million, eight hundred eleven thousand, six hundred sixty-one".