991721119 has 4 divisors (see below), whose sum is σ = 991788840. Its totient is φ = 991653400.

The previous prime is 991721111. The next prime is 991721173. The reversal of 991721119 is 911127199.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 991721119 - 2³ = 991721111 is a prime.

It is a super-2 number, since 2×991721119² = 1967021555741224322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991721111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1732 + ... + 44569.

It is an arithmetic number, because the mean of its divisors is an integer number (247947210).

Almost surely, 2^991721119 is an apocalyptic number.

991721119 is a deficient number, since it is larger than the sum of its proper divisors (67721).

991721119 is a wasteful number, since it uses less digits than its factorization.

991721119 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67720.

The product of its digits is 10206, while the sum is 40.

The square root of 991721119 is about 31491.6039445437. The cubic root of 991721119 is about 997.2327222376.

The spelling of 991721119 in words is "nine hundred ninety-one million, seven hundred twenty-one thousand, one hundred nineteen".