21001121001 has 24 divisors (see below), whose sum is σ = 34719347520. Its totient is φ = 11983045536.

The previous prime is 21001120993. The next prime is 21001121017. The reversal of 21001121001 is 10012110012.

It is a happy number.

It is not a de Polignac number, because 21001121001 - 2³ = 21001120993 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (21001121501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 201006 + ... + 287063.

It is an arithmetic number, because the mean of its divisors is an integer number (1446639480).

Almost surely, 2^21001121001 is an apocalyptic number.

21001121001 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21001121001 is a deficient number, since it is larger than the sum of its proper divisors (13718226519).

21001121001 is a wasteful number, since it uses less digits than its factorization.

21001121001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 488765 (or 488762 counting only the distinct ones).

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

Adding to 21001121001 its reverse (10012110012), we get a palindrome (31013231013).

The spelling of 21001121001 in words is "twenty-one billion, one million, one hundred twenty-one thousand, one".