21101010101021 has 4 divisors (see below), whose sum is σ = 21499142367132. Its totient is φ = 20702877834912.

The previous prime is 21101010100999. The next prime is 21101010101029. The reversal of 21101010101021 is 12010101010112.

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 18203355038521 + 2897655062500 = 4266539^2 + 1702250^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101010101021 - 2¹⁸ = 21101009838877 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21101010100993 and 21101010101011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101010101029) 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, 199066132976 + ... + 199066133081.

It is an arithmetic number, because the mean of its divisors is an integer number (5374785591783).

Almost surely, 2^{21101010101021} is an apocalyptic number.

It is an amenable number.

21101010101021 is a deficient number, since it is larger than the sum of its proper divisors (398132266111).

21101010101021 is an equidigital number, since it uses as much as digits as its factorization.

21101010101021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398132266110.

The product of its (nonzero) digits is 4, while the sum is 11.

Adding to 21101010101021 its reverse (12010101010112), we get a palindrome (33111111111133).

Subtracting from 21101010101021 its reverse (12010101010112), we obtain a palindrome (9090909090909).

The spelling of 21101010101021 in words is "twenty-one trillion, one hundred one billion, ten million, one hundred one thousand, twenty-one".