2123540821 has 4 divisors (see below), whose sum is σ = 2126332044. Its totient is φ = 2120749600.

The previous prime is 2123540791. The next prime is 2123540831. The reversal of 2123540821 is 1280453212.

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 1027202500 + 1096338321 = 32050^2 + 33111^2 .

It is a cyclic number.

It is not a de Polignac number, because 2123540821 - 2¹³ = 2123532629 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 2123540821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2123540831) 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, 1394470 + ... + 1395991.

It is an arithmetic number, because the mean of its divisors is an integer number (531583011).

Almost surely, 2^2123540821 is an apocalyptic number.

It is an amenable number.

2123540821 is a deficient number, since it is larger than the sum of its proper divisors (2791223).

2123540821 is an equidigital number, since it uses as much as digits as its factorization.

2123540821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2791222.

The product of its (nonzero) digits is 3840, while the sum is 28.

The square root of 2123540821 is about 46081.8925501113. The cubic root of 2123540821 is about 1285.3464565670.

The spelling of 2123540821 in words is "two billion, one hundred twenty-three million, five hundred forty thousand, eight hundred twenty-one".