2121821 has 8 divisors (see below), whose sum is σ = 2419704. Its totient is φ = 1843200.

The previous prime is 2121809. The next prime is 2121829. The reversal of 2121821 is 1281212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 470596 + 1651225 = 686^2 + 1285^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2121821 - 2¹⁸ = 1859677 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

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 2121821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2121829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4580 + ... + 5021.

It is an arithmetic number, because the mean of its divisors is an integer number (302463).

2^2121821 is an apocalyptic number.

It is an amenable number.

2121821 is a deficient number, since it is larger than the sum of its proper divisors (297883).

2121821 is a wasteful number, since it uses less digits than its factorization.

2121821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9631.

The product of its digits is 64, while the sum is 17.

The square root of 2121821 is about 1456.6471775966. The cubic root of 2121821 is about 128.4999369155.

The spelling of 2121821 in words is "two million, one hundred twenty-one thousand, eight hundred twenty-one".