21011020010021 has 4 divisors (see below), whose sum is σ = 21011059484844. Its totient is φ = 21010980535200.

The previous prime is 21011020010017. The next prime is 21011020010069. The reversal of 21011020010021 is 12001002011012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8310449356225 + 12700570653796 = 2882785^2 + 3563786^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011020010021 - 2² = 21011020010017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011020009984 and 21011020010011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011020010011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18927950 + ... + 20007231.

It is an arithmetic number, because the mean of its divisors is an integer number (5252764871211).

Almost surely, 2^{21011020010021} is an apocalyptic number.

It is an amenable number.

21011020010021 is a deficient number, since it is larger than the sum of its proper divisors (39474823).

21011020010021 is an equidigital number, since it uses as much as digits as its factorization.

21011020010021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39474822.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21011020010021 its reverse (12001002011012), we get a palindrome (33012022021033).

The spelling of 21011020010021 in words is "twenty-one trillion, eleven billion, twenty million, ten thousand, twenty-one".