2091818021 has 4 divisors (see below), whose sum is σ = 2092463532. Its totient is φ = 2091172512.

The previous prime is 2091817999. The next prime is 2091818077. The reversal of 2091818021 is 1208181902.

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 1311453796 + 780364225 = 36214^2 + 27935^2 .

It is a cyclic number.

It is not a de Polignac number, because 2091818021 - 2³⁰ = 1018076197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2091815021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 317870 + ... + 324383.

It is an arithmetic number, because the mean of its divisors is an integer number (523115883).

Almost surely, 2^2091818021 is an apocalyptic number.

It is an amenable number.

2091818021 is a deficient number, since it is larger than the sum of its proper divisors (645511).

2091818021 is an equidigital number, since it uses as much as digits as its factorization.

2091818021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 645510.

The product of its (nonzero) digits is 2304, while the sum is 32.

The square root of 2091818021 is about 45736.3971143334. The cubic root of 2091818021 is about 1278.9138778446.

Adding to 2091818021 its reverse (1208181902), we get a palindrome (3299999923).

The spelling of 2091818021 in words is "two billion, ninety-one million, eight hundred eighteen thousand, twenty-one".