21020200021 has 8 divisors (see below), whose sum is σ = 21309412824. Its totient is φ = 20732467200.

The previous prime is 21020199989. The next prime is 21020200057. The reversal of 21020200021 is 12000202012.

It can be written as a sum of positive squares in 4 ways, for example, as 15528648996 + 5491551025 = 124614^2 + 74105^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21020200021 - 2⁵ = 21020199989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21020199980 and 21020200007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020200081) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 341380 + ... + 398221.

It is an arithmetic number, because the mean of its divisors is an integer number (2663676603).

Almost surely, 2^21020200021 is an apocalyptic number.

It is an amenable number.

21020200021 is a deficient number, since it is larger than the sum of its proper divisors (289212803).

21020200021 is an equidigital number, since it uses as much as digits as its factorization.

21020200021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 739991.

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21020200021 its reverse (12000202012), we get a palindrome (33020402033).

The spelling of 21020200021 in words is "twenty-one billion, twenty million, two hundred thousand, twenty-one".