1911811721 has 4 divisors (see below), whose sum is σ = 2024271252. Its totient is φ = 1799352192.

The previous prime is 1911811663. The next prime is 1911811723. The reversal of 1911811721 is 1271181191.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1510410496 + 401401225 = 38864^2 + 20035^2 .

It is a cyclic number.

It is not a de Polignac number, because 1911811721 - 2¹⁰ = 1911810697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1911811723) 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, 56229740 + ... + 56229773.

It is an arithmetic number, because the mean of its divisors is an integer number (506067813).

Almost surely, 2^1911811721 is an apocalyptic number.

It is an amenable number.

1911811721 is a deficient number, since it is larger than the sum of its proper divisors (112459531).

1911811721 is a wasteful number, since it uses less digits than its factorization.

1911811721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112459530.

The product of its digits is 1008, while the sum is 32.

The square root of 1911811721 is about 43724.2692448942. The cubic root of 1911811721 is about 1241.1236175469.

The spelling of 1911811721 in words is "one billion, nine hundred eleven million, eight hundred eleven thousand, seven hundred twenty-one".