21220021021 has 4 divisors (see below), whose sum is σ = 21224329344. Its totient is φ = 21215712700.

The previous prime is 21220021003. The next prime is 21220021033. The reversal of 21220021021 is 12012002212.

It is a happy number.

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 21220021021 - 2⁵ = 21220020989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21220020992 and 21220021010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220021001) 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, 2146765 + ... + 2156626.

It is an arithmetic number, because the mean of its divisors is an integer number (5306082336).

Almost surely, 2^21220021021 is an apocalyptic number.

It is an amenable number.

21220021021 is a deficient number, since it is larger than the sum of its proper divisors (4308323).

21220021021 is an equidigital number, since it uses as much as digits as its factorization.

21220021021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4308322.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21220021021 its reverse (12012002212), we get a palindrome (33232023233).

The spelling of 21220021021 in words is "twenty-one billion, two hundred twenty million, twenty-one thousand, twenty-one".