2123921 has 4 divisors (see below), whose sum is σ = 2136372. Its totient is φ = 2111472.

The previous prime is 2123917. The next prime is 2123939. The reversal of 2123921 is 1293212.

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 1050625 + 1073296 = 1025^2 + 1036^2 .

It is a cyclic number.

It is not a de Polignac number, because 2123921 - 2² = 2123917 is a prime.

It is a super-2 number, since 2×2123921² = 9022080828482, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2123893 and 2123902.

It is not an unprimeable number, because it can be changed into a prime (2123971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5966 + ... + 6311.

It is an arithmetic number, because the mean of its divisors is an integer number (534093).

2^2123921 is an apocalyptic number.

It is an amenable number.

2123921 is a deficient number, since it is larger than the sum of its proper divisors (12451).

2123921 is a wasteful number, since it uses less digits than its factorization.

2123921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12450.

The product of its digits is 216, while the sum is 20.

The square root of 2123921 is about 1457.3678327725. The cubic root of 2123921 is about 128.5423157482.

The spelling of 2123921 in words is "two million, one hundred twenty-three thousand, nine hundred twenty-one".