21001212110021 has 32 divisors (see below), whose sum is σ = 25974205985280. Its totient is φ = 16693991524800.

The previous prime is 21001212109967. The next prime is 21001212110027. The reversal of 21001212110021 is 12001121210012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001212110021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001212109978 and 21001212110005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001212110027) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 24275126 + ... + 25125368.

It is an arithmetic number, because the mean of its divisors is an integer number (811693937040).

Almost surely, 2^{21001212110021} is an apocalyptic number.

It is an amenable number.

21001212110021 is a deficient number, since it is larger than the sum of its proper divisors (4972993875259).

21001212110021 is a wasteful number, since it uses less digits than its factorization.

21001212110021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 859377.

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

Adding to 21001212110021 its reverse (12001121210012), we get a palindrome (33002333320033).

Subtracting from 21001212110021 its reverse (12001121210012), we obtain a palindrome (9000090900009).

It can be divided in two parts, 2100 and 1212110021, that added together give a palindrome (1212112121).

The spelling of 21001212110021 in words is "twenty-one trillion, one billion, two hundred twelve million, one hundred ten thousand, twenty-one".