21011201021 has 4 divisors (see below), whose sum is σ = 21026640444. Its totient is φ = 20995761600.

The previous prime is 21011201011. The next prime is 21011201027. The reversal of 21011201021 is 12010211012.

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 6656764921 + 14354436100 = 81589^2 + 119810^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011201021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011200993 and 21011201011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011201027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7717670 + ... + 7720391.

It is an arithmetic number, because the mean of its divisors is an integer number (5256660111).

Almost surely, 2^21011201021 is an apocalyptic number.

It is an amenable number.

21011201021 is a deficient number, since it is larger than the sum of its proper divisors (15439423).

21011201021 is a wasteful number, since it uses less digits than its factorization.

21011201021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15439422.

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

Adding to 21011201021 its reverse (12010211012), we get a palindrome (33021412033).

Subtracting from 21011201021 its reverse (12010211012), we obtain a palindrome (9000990009).

The spelling of 21011201021 in words is "twenty-one billion, eleven million, two hundred one thousand, twenty-one".