21001021121 has 4 divisors (see below), whose sum is σ = 21117049044. Its totient is φ = 20884993200.

The previous prime is 21001021103. The next prime is 21001021123. The reversal of 21001021121 is 12112010012.

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 4786564225 + 16214456896 = 69185^2 + 127336^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001021121 - 2²² = 20996826817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001021123) 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, 58013690 + ... + 58014051.

It is an arithmetic number, because the mean of its divisors is an integer number (5279262261).

Almost surely, 2^21001021121 is an apocalyptic number.

It is an amenable number.

21001021121 is a deficient number, since it is larger than the sum of its proper divisors (116027923).

21001021121 is a wasteful number, since it uses less digits than its factorization.

21001021121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116027922.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21001021121 its reverse (12112010012), we get a palindrome (33113031133).

The spelling of 21001021121 in words is "twenty-one billion, one million, twenty-one thousand, one hundred twenty-one".