2125721 has 4 divisors (see below), whose sum is σ = 2289252. Its totient is φ = 1962192.

The previous prime is 2125703. The next prime is 2125733. The reversal of 2125721 is 1275212.

2125721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 1000000 + 1125721 = 1000^2 + 1061^2 .

It is a cyclic number.

It is not a de Polignac number, because 2125721 - 2⁶ = 2125657 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2125693 and 2125702.

It is not an unprimeable number, because it can be changed into a prime (2125741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 81746 + ... + 81771.

It is an arithmetic number, because the mean of its divisors is an integer number (572313).

2^2125721 is an apocalyptic number.

It is an amenable number.

2125721 is a deficient number, since it is larger than the sum of its proper divisors (163531).

2125721 is a wasteful number, since it uses less digits than its factorization.

2125721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163530.

The product of its digits is 280, while the sum is 20.

The square root of 2125721 is about 1457.9852536977. The cubic root of 2125721 is about 128.5786182340.

It can be divided in two parts, 2125 and 721, that multiplied together give a triangular number (1532125 = T₁₇₅₀).

The spelling of 2125721 in words is "two million, one hundred twenty-five thousand, seven hundred twenty-one".