21001120421 has 2 divisors, whose sum is σ = 21001120422. Its totient is φ = 21001120420.

The previous prime is 21001120417. The next prime is 21001120429. The reversal of 21001120421 is 12402110012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20975728900 + 25391521 = 144830^2 + 5039^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001120421 - 2² = 21001120417 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21001120396 and 21001120405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21001120429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500560210 + 10500560211.

It is an arithmetic number, because the mean of its divisors is an integer number (10500560211).

Almost surely, 2^21001120421 is an apocalyptic number.

It is an amenable number.

21001120421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001120421 is an equidigital number, since it uses as much as digits as its factorization.

21001120421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21001120421 its reverse (12402110012), we get a palindrome (33403230433).

The spelling of 21001120421 in words is "twenty-one billion, one million, one hundred twenty thousand, four hundred twenty-one".