21120220021 has 4 divisors (see below), whose sum is σ = 21848503500. Its totient is φ = 20391936544.

The previous prime is 21120219983. The next prime is 21120220039. The reversal of 21120220021 is 12002202112.

It is a happy number.

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 13756005796 + 7364214225 = 117286^2 + 85815^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120220021 - 2⁹ = 21120219509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21120219983 and 21120220010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120220721) 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, 364141696 + ... + 364141753.

It is an arithmetic number, because the mean of its divisors is an integer number (5462125875).

Almost surely, 2^21120220021 is an apocalyptic number.

It is an amenable number.

21120220021 is a deficient number, since it is larger than the sum of its proper divisors (728283479).

21120220021 is an equidigital number, since it uses as much as digits as its factorization.

21120220021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 728283478.

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

Adding to 21120220021 its reverse (12002202112), we get a palindrome (33122422133).

The spelling of 21120220021 in words is "twenty-one billion, one hundred twenty million, two hundred twenty thousand, twenty-one".