21106102561 has 4 divisors (see below), whose sum is σ = 21106454292. Its totient is φ = 21105750832.

The previous prime is 21106102547. The next prime is 21106102601. The reversal of 21106102561 is 16520160112.

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 20091361536 + 1014741025 = 141744^2 + 31855^2 .

It is a cyclic number.

It is not a de Polignac number, because 21106102561 - 2³³ = 12516167969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21106102261) 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, 60730 + ... + 214243.

It is an arithmetic number, because the mean of its divisors is an integer number (5276613573).

Almost surely, 2^21106102561 is an apocalyptic number.

It is an amenable number.

21106102561 is a deficient number, since it is larger than the sum of its proper divisors (351731).

21106102561 is an equidigital number, since it uses as much as digits as its factorization.

21106102561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351730.

The product of its (nonzero) digits is 720, while the sum is 25.

Adding to 21106102561 its reverse (16520160112), we get a palindrome (37626262673).

The spelling of 21106102561 in words is "twenty-one billion, one hundred six million, one hundred two thousand, five hundred sixty-one".