21111010021021 has 4 divisors (see below), whose sum is σ = 21186138170844. Its totient is φ = 21035881871200.

The previous prime is 21111010020979. The next prime is 21111010021097. The reversal of 21111010021021 is 12012001011112.

It is a happy number.

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 17857005320025 + 3254004700996 = 4225755^2 + 1803886^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111010021021 - 2³⁷ = 20973571067549 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111010020992 and 21111010021010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111010021921) 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, 37564074490 + ... + 37564075051.

It is an arithmetic number, because the mean of its divisors is an integer number (5296534542711).

Almost surely, 2^{21111010021021} is an apocalyptic number.

It is an amenable number.

21111010021021 is a deficient number, since it is larger than the sum of its proper divisors (75128149823).

21111010021021 is an equidigital number, since it uses as much as digits as its factorization.

21111010021021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75128149822.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21111010021021 its reverse (12012001011112), we get a palindrome (33123011032133).

Subtracting from 21111010021021 its reverse (12012001011112), we obtain a palindrome (9099009009909).

The spelling of 21111010021021 in words is "twenty-one trillion, one hundred eleven billion, ten million, twenty-one thousand, twenty-one".