202121200021 has 4 divisors (see below), whose sum is σ = 217668984652. Its totient is φ = 186573415392.

The previous prime is 202121200019. The next prime is 202121200051. The reversal of 202121200021 is 120002121202.

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 18363231121 + 183757968900 = 135511^2 + 428670^2 .

It is not a de Polignac number, because 202121200021 - 2¹ = 202121200019 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13), and also a Moran number because the ratio is a prime number: 15547784617 = 202121200021 / (2 + 0 + 2 + 1 + 2 + 1 + 2 + 0 + 0 + 0 + 2 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 202121199974 and 202121200010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (202121200051) 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, 7773892296 + ... + 7773892321.

It is an arithmetic number, because the mean of its divisors is an integer number (54417246163).

Almost surely, 2^202121200021 is an apocalyptic number.

It is an amenable number.

202121200021 is a deficient number, since it is larger than the sum of its proper divisors (15547784631).

202121200021 is a wasteful number, since it uses less digits than its factorization.

202121200021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15547784630.

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

Adding to 202121200021 its reverse (120002121202), we get a palindrome (322123321223).

The spelling of 202121200021 in words is "two hundred two billion, one hundred twenty-one million, two hundred thousand, twenty-one".