21001100000121 has 16 divisors (see below), whose sum is σ = 31118495116800. Its totient is φ = 13998143864304.

The previous prime is 21001100000093. The next prime is 21001100000123. The reversal of 21001100000121 is 12100000110012.

It is a happy number.

It is not a de Polignac number, because 21001100000121 - 2⁶ = 21001100000057 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 (21001100000123) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71781006 + ... + 72072983.

It is an arithmetic number, because the mean of its divisors is an integer number (1944905944800).

Almost surely, 2^{21001100000121} is an apocalyptic number.

It is an amenable number.

21001100000121 is a deficient number, since it is larger than the sum of its proper divisors (10117395116679).

21001100000121 is a wasteful number, since it uses less digits than its factorization.

21001100000121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143859405 (or 143859399 counting only the distinct ones).

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

Adding to 21001100000121 its reverse (12100000110012), we get a palindrome (33101100110133).

The spelling of 21001100000121 in words is "twenty-one trillion, one billion, one hundred million, one hundred twenty-one", and thus it is an aban number.