10891721 has 4 divisors (see below), whose sum is σ = 11054352. Its totient is φ = 10729092.

The previous prime is 10891717. The next prime is 10891723. The reversal of 10891721 is 12719801.

10891721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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: 12719801 = 2029 ⋅6269.

It is a cyclic number.

It is not a de Polignac number, because 10891721 - 2² = 10891717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (10891723) 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 3 ways as a sum of consecutive naturals, for example, 81215 + ... + 81348.

It is an arithmetic number, because the mean of its divisors is an integer number (2763588).

Almost surely, 2^10891721 is an apocalyptic number.

It is an amenable number.

10891721 is a deficient number, since it is larger than the sum of its proper divisors (162631).

10891721 is an equidigital number, since it uses as much as digits as its factorization.

10891721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162630.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 10891721 is about 3300.2607472744. The cubic root of 10891721 is about 221.6658732015.

The spelling of 10891721 in words is "ten million, eight hundred ninety-one thousand, seven hundred twenty-one".