2138821 has 4 divisors (see below), whose sum is σ = 2264652. Its totient is φ = 2012992.

The previous prime is 2138813. The next prime is 2138831. The reversal of 2138821 is 1288312.

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 662596 + 1476225 = 814^2 + 1215^2 .

It is a cyclic number.

It is not a de Polignac number, because 2138821 - 2³ = 2138813 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 (2138831) 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, 62890 + ... + 62923.

It is an arithmetic number, because the mean of its divisors is an integer number (566163).

2^2138821 is an apocalyptic number.

It is an amenable number.

2138821 is a deficient number, since it is larger than the sum of its proper divisors (125831).

2138821 is a wasteful number, since it uses less digits than its factorization.

2138821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125830.

The product of its digits is 768, while the sum is 25.

The square root of 2138821 is about 1462.4708544104. The cubic root of 2138821 is about 128.8422043514.

The spelling of 2138821 in words is "two million, one hundred thirty-eight thousand, eight hundred twenty-one".