2195821 has 4 divisors (see below), whose sum is σ = 2198812. Its totient is φ = 2192832.

The previous prime is 2195819. The next prime is 2195827. The reversal of 2195821 is 1285912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1726596 + 469225 = 1314^2 + 685^2 .

It is a cyclic number.

It is not a de Polignac number, because 2195821 - 2¹ = 2195819 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 2195821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2195827) 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, 451 + ... + 2143.

It is an arithmetic number, because the mean of its divisors is an integer number (549703).

2^2195821 is an apocalyptic number.

It is an amenable number.

2195821 is a deficient number, since it is larger than the sum of its proper divisors (2991).

2195821 is a wasteful number, since it uses less digits than its factorization.

2195821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2990.

The product of its digits is 1440, while the sum is 28.

The square root of 2195821 is about 1481.8302871787. The cubic root of 2195821 is about 129.9767414011.

Subtracting from 2195821 its reverse (1285912), we obtain a palindrome (909909).

The spelling of 2195821 in words is "two million, one hundred ninety-five thousand, eight hundred twenty-one".