20404120021 has 2 divisors, whose sum is σ = 20404120022. Its totient is φ = 20404120020.

The previous prime is 20404119959. The next prime is 20404120097. The reversal of 20404120021 is 12002140402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18937612996 + 1466507025 = 137614^2 + 38295^2 .

It is a cyclic number.

It is not a de Polignac number, because 20404120021 - 2¹¹ = 20404117973 is a prime.

It is a super-2 number, since 2×20404120021² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20404119977 and 20404120004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20404120421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10202060010 + 10202060011.

It is an arithmetic number, because the mean of its divisors is an integer number (10202060011).

Almost surely, 2^20404120021 is an apocalyptic number.

It is an amenable number.

20404120021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20404120021 is an equidigital number, since it uses as much as digits as its factorization.

20404120021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 16.

Adding to 20404120021 its reverse (12002140402), we get a palindrome (32406260423).

The spelling of 20404120021 in words is "twenty billion, four hundred four million, one hundred twenty thousand, twenty-one".