21001001121 has 24 divisors (see below), whose sum is σ = 30698202080. Its totient is φ = 13833892800.

The previous prime is 21001001111. The next prime is 21001001141. The reversal of 21001001121 is 12110010012.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21001001121 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001001111) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 224181 + ... + 303741.

Almost surely, 2^21001001121 is an apocalyptic number.

It is an amenable number.

21001001121 is a deficient number, since it is larger than the sum of its proper divisors (9697200959).

21001001121 is a wasteful number, since it uses less digits than its factorization.

21001001121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79917 (or 79914 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21001001121 its reverse (12110010012), we get a palindrome (33111011133).

The spelling of 21001001121 in words is "twenty-one billion, one million, one thousand, one hundred twenty-one".