21156110161 has 4 divisors (see below), whose sum is σ = 21159731824. Its totient is φ = 21152488500.

The previous prime is 21156110147. The next prime is 21156110203. The reversal of 21156110161 is 16101165112.

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 21156110161 - 2⁹ = 21156109649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21156110111) 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, 1802055 + ... + 1813756.

It is an arithmetic number, because the mean of its divisors is an integer number (5289932956).

Almost surely, 2^21156110161 is an apocalyptic number.

It is an amenable number.

21156110161 is a deficient number, since it is larger than the sum of its proper divisors (3621663).

21156110161 is an equidigital number, since it uses as much as digits as its factorization.

21156110161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3621662.

The product of its (nonzero) digits is 360, while the sum is 25.

Adding to 21156110161 its reverse (16101165112), we get a palindrome (37257275273).

The spelling of 21156110161 in words is "twenty-one billion, one hundred fifty-six million, one hundred ten thousand, one hundred sixty-one".