21011101021 has 4 divisors (see below), whose sum is σ = 21019620352. Its totient is φ = 21002581692.

The previous prime is 21011101009. The next prime is 21011101103. The reversal of 21011101021 is 12010111012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21011101021 - 2¹⁹ = 21010576733 is a prime.

It is a super-2 number, since 2×21011101021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011100989 and 21011101007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011104021) 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, 4255965 + ... + 4260898.

It is an arithmetic number, because the mean of its divisors is an integer number (5254905088).

Almost surely, 2^21011101021 is an apocalyptic number.

It is an amenable number.

21011101021 is a deficient number, since it is larger than the sum of its proper divisors (8519331).

21011101021 is an equidigital number, since it uses as much as digits as its factorization.

21011101021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8519330.

The product of its (nonzero) digits is 4, while the sum is 10.

Adding to 21011101021 its reverse (12010111012), we get a palindrome (33021212033).

Subtracting from 21011101021 its reverse (12010111012), we obtain a palindrome (9000990009).

The spelling of 21011101021 in words is "twenty-one billion, eleven million, one hundred one thousand, twenty-one".