21220161 has 4 divisors (see below), whose sum is σ = 28293552. Its totient is φ = 14146772.

The previous prime is 21220159. The next prime is 21220211. The reversal of 21220161 is 16102212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21220161 - 2¹ = 21220159 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21220161.

It is not an unprimeable number, because it can be changed into a prime (21220261) 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, 3536691 + ... + 3536696.

It is an arithmetic number, because the mean of its divisors is an integer number (7073388).

Almost surely, 2^21220161 is an apocalyptic number.

It is an amenable number.

21220161 is a deficient number, since it is larger than the sum of its proper divisors (7073391).

21220161 is an equidigital number, since it uses as much as digits as its factorization.

21220161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7073390.

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21220161 is about 4606.5345977209. The cubic root of 21220161 is about 276.8532067256.

Adding to 21220161 its reverse (16102212), we get a palindrome (37322373).

The spelling of 21220161 in words is "twenty-one million, two hundred twenty thousand, one hundred sixty-one".