21011121121 has 8 divisors (see below), whose sum is σ = 21303109640. Its totient is φ = 20719245312.

The previous prime is 21011121073. The next prime is 21011121127. The reversal of 21011121121 is 12112111012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8798440000 + 12212681121 = 93800^2 + 110511^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21011121121 - 2⁷ = 21011120993 is a prime.

It is a super-2 number, since 2×21011121121² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21011121127) 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, 390001 + ... + 440593.

It is an arithmetic number, because the mean of its divisors is an integer number (2662888705).

Almost surely, 2^21011121121 is an apocalyptic number.

It is an amenable number.

21011121121 is a deficient number, since it is larger than the sum of its proper divisors (291988519).

21011121121 is an equidigital number, since it uses as much as digits as its factorization.

21011121121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56355.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21011121121 its reverse (12112111012), we get a palindrome (33123232133).

The spelling of 21011121121 in words is "twenty-one billion, eleven million, one hundred twenty-one thousand, one hundred twenty-one".