21011012021 has 4 divisors (see below), whose sum is σ = 21011473152. Its totient is φ = 21010550892.

The previous prime is 21011011997. The next prime is 21011012027. The reversal of 21011012021 is 12021011012.

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 a de Polignac number, because none of the positive numbers 2^k-21011012021 is a prime.

It is a super-2 number, since 2×21011012021² (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 = 21011011993 and 21011012011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011012027) 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, 153671 + ... + 256196.

It is an arithmetic number, because the mean of its divisors is an integer number (5252868288).

Almost surely, 2^21011012021 is an apocalyptic number.

It is an amenable number.

21011012021 is a deficient number, since it is larger than the sum of its proper divisors (461131).

21011012021 is an equidigital number, since it uses as much as digits as its factorization.

21011012021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 461130.

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

Adding to 21011012021 its reverse (12021011012), we get a palindrome (33032023033).

The spelling of 21011012021 in words is "twenty-one billion, eleven million, twelve thousand, twenty-one".