21821189 has 4 divisors (see below), whose sum is σ = 23499756. Its totient is φ = 20142624.

The previous prime is 21821171. The next prime is 21821197. The reversal of 21821189 is 98112812.

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 8168164 + 13653025 = 2858^2 + 3695^2 .

It is a cyclic number.

It is not a de Polignac number, because 21821189 - 2⁸ = 21820933 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 (21821119) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 839264 + ... + 839289.

It is an arithmetic number, because the mean of its divisors is an integer number (5874939).

Almost surely, 2^21821189 is an apocalyptic number.

It is an amenable number.

21821189 is a deficient number, since it is larger than the sum of its proper divisors (1678567).

21821189 is a wasteful number, since it uses less digits than its factorization.

21821189 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1678566.

The product of its digits is 2304, while the sum is 32.

The square root of 21821189 is about 4671.3155534603. The cubic root of 21821189 is about 279.4427223812.

The spelling of 21821189 in words is "twenty-one million, eight hundred twenty-one thousand, one hundred eighty-nine".