21121101605 has 8 divisors (see below), whose sum is σ = 25350906264. Its totient is φ = 16893158400.

The previous prime is 21121101601. The next prime is 21121101647. The reversal of 21121101605 is 50610112112.

It can be written as a sum of positive squares in 4 ways, for example, as 499567201 + 20621534404 = 22351^2 + 143602^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21121101605 - 2² = 21121101601 is a prime.

It is a super-2 number, since 2×21121101605² (a number of 21 digits) 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 (21121101601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 440276 + ... + 485885.

It is an arithmetic number, because the mean of its divisors is an integer number (3168863283).

Almost surely, 2^21121101605 is an apocalyptic number.

It is an amenable number.

21121101605 is a deficient number, since it is larger than the sum of its proper divisors (4229804659).

21121101605 is an equidigital number, since it uses as much as digits as its factorization.

21121101605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 930727.

The product of its (nonzero) digits is 120, while the sum is 20.

Adding to 21121101605 its reverse (50610112112), we get a palindrome (71731213717).

The spelling of 21121101605 in words is "twenty-one billion, one hundred twenty-one million, one hundred one thousand, six hundred five".