21022181 has 4 divisors (see below), whose sum is σ = 21208332. Its totient is φ = 20836032.

The previous prime is 21022171. The next prime is 21022193. The reversal of 21022181 is 18122012.

It is a happy number.

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 6076225 + 14945956 = 2465^2 + 3866^2 .

It is a cyclic number.

It is not a de Polignac number, because 21022181 - 2⁶ = 21022117 is a prime.

It is a super-2 number, since 2×21022181² = 883864187993522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21022171) 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, 92906 + ... + 93131.

It is an arithmetic number, because the mean of its divisors is an integer number (5302083).

Almost surely, 2^21022181 is an apocalyptic number.

It is an amenable number.

21022181 is a deficient number, since it is larger than the sum of its proper divisors (186151).

21022181 is a wasteful number, since it uses less digits than its factorization.

21022181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186150.

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

The square root of 21022181 is about 4584.9952017423. The cubic root of 21022181 is about 275.9895194858.

Adding to 21022181 its reverse (18122012), we get a palindrome (39144193).

The spelling of 21022181 in words is "twenty-one million, twenty-two thousand, one hundred eighty-one".