21202020021 has 16 divisors (see below), whose sum is σ = 34793058944. Its totient is φ = 11183482944.

The previous prime is 21202020013. The next prime is 21202020041. The reversal of 21202020021 is 12002020212.

It is not a de Polignac number, because 21202020021 - 2³ = 21202020013 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21202019979 and 21202020006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21202020041) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38831266 + ... + 38831811.

It is an arithmetic number, because the mean of its divisors is an integer number (2174566184).

Almost surely, 2^21202020021 is an apocalyptic number.

21202020021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21202020021 is a deficient number, since it is larger than the sum of its proper divisors (13591038923).

21202020021 is a wasteful number, since it uses less digits than its factorization.

21202020021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77663100.

The product of its (nonzero) digits is 32, while the sum is 12.

Adding to 21202020021 its reverse (12002020212), we get a palindrome (33204040233).

The spelling of 21202020021 in words is "twenty-one billion, two hundred two million, twenty thousand, twenty-one".