21124312021 has 2 divisors, whose sum is σ = 21124312022. Its totient is φ = 21124312020.

The previous prime is 21124312019. The next prime is 21124312067. The reversal of 21124312021 is 12021342112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16106148100 + 5018163921 = 126910^2 + 70839^2 .

It is a cyclic number.

It is not a de Polignac number, because 21124312021 - 2¹ = 21124312019 is a prime.

Together with 21124312019, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21124312021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21124316021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562156010 + 10562156011.

It is an arithmetic number, because the mean of its divisors is an integer number (10562156011).

Almost surely, 2^21124312021 is an apocalyptic number.

It is an amenable number.

21124312021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21124312021 is an equidigital number, since it uses as much as digits as its factorization.

21124312021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 19.

Adding to 21124312021 its reverse (12021342112), we get a palindrome (33145654133).

The spelling of 21124312021 in words is "twenty-one billion, one hundred twenty-four million, three hundred twelve thousand, twenty-one".