1091721 has 16 divisors (see below), whose sum is σ = 1555200. Its totient is φ = 679248.

The previous prime is 1091711. The next prime is 1091729. The reversal of 1091721 is 1271901.

It is not a de Polignac number, because 1091721 - 2¹⁰ = 1090697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1091729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6010 + ... + 6188.

It is an arithmetic number, because the mean of its divisors is an integer number (97200).

2^1091721 is an apocalyptic number.

It is an amenable number.

1091721 is a deficient number, since it is larger than the sum of its proper divisors (463479).

1091721 is a wasteful number, since it uses less digits than its factorization.

1091721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308.

The product of its (nonzero) digits is 126, while the sum is 21.

The square root of 1091721 is about 1044.8545353302. The cubic root of 1091721 is about 102.9683819123.

It can be divided in two parts, 109 and 1721, that added together give a triangular number (1830 = T₆₀).

The spelling of 1091721 in words is "one million, ninety-one thousand, seven hundred twenty-one".