891668729 has 6 divisors (see below), whose sum is σ = 1037247354. Its totient is φ = 764287440.

The previous prime is 891668633. The next prime is 891668731. The reversal of 891668729 is 927866198.

It can be written as a sum of positive squares in only one way, i.e., 890903104 + 765625 = 29848^2 + 875^2 .

It is not a de Polignac number, because 891668729 - 2²⁰ = 890620153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (891668929) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9098612 + ... + 9098709.

It is an arithmetic number, because the mean of its divisors is an integer number (172874559).

Almost surely, 2^891668729 is an apocalyptic number.

It is an amenable number.

891668729 is a deficient number, since it is larger than the sum of its proper divisors (145578625).

891668729 is a wasteful number, since it uses less digits than its factorization.

891668729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18197335 (or 18197328 counting only the distinct ones).

The product of its digits is 2612736, while the sum is 56.

The square root of 891668729 is about 29860.8226443948. The cubic root of 891668729 is about 962.5009763075.

The spelling of 891668729 in words is "eight hundred ninety-one million, six hundred sixty-eight thousand, seven hundred twenty-nine".