21020200121 has 4 divisors (see below), whose sum is σ = 21022010100. Its totient is φ = 21018390144.

The previous prime is 21020200081. The next prime is 21020200127. The reversal of 21020200121 is 12100202012.

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 13216951225 + 7803248896 = 114965^2 + 88336^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020200121 - 2⁶ = 21020200057 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21020200127) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 887456 + ... + 910833.

It is an arithmetic number, because the mean of its divisors is an integer number (5255502525).

Almost surely, 2^21020200121 is an apocalyptic number.

It is an amenable number.

21020200121 is a deficient number, since it is larger than the sum of its proper divisors (1809979).

21020200121 is a wasteful number, since it uses less digits than its factorization.

21020200121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1809978.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21020200121 its reverse (12100202012), we get a palindrome (33120402133).

The spelling of 21020200121 in words is "twenty-one billion, twenty million, two hundred thousand, one hundred twenty-one".