21001121120021 has 16 divisors (see below), whose sum is σ = 24122874123264. Its totient is φ = 17909968765824.

The previous prime is 21001121119991. The next prime is 21001121120129. The reversal of 21001121120021 is 12002112110012.

It is a cyclic number.

It is not a de Polignac number, because 21001121120021 - 2³⁴ = 20983941250837 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001121119978 and 21001121120005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001121126021) 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, 7189520 + ... + 9679433.

It is an arithmetic number, because the mean of its divisors is an integer number (1507679632704).

Almost surely, 2^{21001121120021} is an apocalyptic number.

It is an amenable number.

21001121120021 is a deficient number, since it is larger than the sum of its proper divisors (3121753003243).

21001121120021 is a wasteful number, since it uses less digits than its factorization.

21001121120021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16869860.

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21001121120021 its reverse (12002112110012), we get a palindrome (33003233230033).

The spelling of 21001121120021 in words is "twenty-one trillion, one billion, one hundred twenty-one million, one hundred twenty thousand, twenty-one".