2121821791 has 4 divisors (see below), whose sum is σ = 2173573584. Its totient is φ = 2070070000.

The previous prime is 2121821777. The next prime is 2121821797. The reversal of 2121821791 is 1971281212.

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

It is a cyclic number.

It is not a de Polignac number, because 2121821791 - 2¹¹ = 2121819743 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 (2121821797) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25875835 + ... + 25875916.

It is an arithmetic number, because the mean of its divisors is an integer number (543393396).

Almost surely, 2^2121821791 is an apocalyptic number.

2121821791 is a deficient number, since it is larger than the sum of its proper divisors (51751793).

2121821791 is an equidigital number, since it uses as much as digits as its factorization.

2121821791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51751792.

The product of its digits is 4032, while the sum is 34.

The square root of 2121821791 is about 46063.2368706325. The cubic root of 2121821791 is about 1284.9995288345. Note that the first 3 decimals are identical.

The spelling of 2121821791 in words is "two billion, one hundred twenty-one million, eight hundred twenty-one thousand, seven hundred ninety-one".