21122320161 has 4 divisors (see below), whose sum is σ = 28163093552. Its totient is φ = 14081546772.

The previous prime is 21122320133. The next prime is 21122320169. The reversal of 21122320161 is 16102322112.

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 not a de Polignac number, because 21122320161 - 2⁶ = 21122320097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21122320169) 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, 3520386691 + ... + 3520386696.

It is an arithmetic number, because the mean of its divisors is an integer number (7040773388).

Almost surely, 2^21122320161 is an apocalyptic number.

It is an amenable number.

21122320161 is a deficient number, since it is larger than the sum of its proper divisors (7040773391).

21122320161 is an equidigital number, since it uses as much as digits as its factorization.

21122320161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7040773390.

The product of its (nonzero) digits is 288, while the sum is 21.

Adding to 21122320161 its reverse (16102322112), we get a palindrome (37224642273).

The spelling of 21122320161 in words is "twenty-one billion, one hundred twenty-two million, three hundred twenty thousand, one hundred sixty-one".