21023545421 has 2 divisors, whose sum is σ = 21023545422. Its totient is φ = 21023545420.

The previous prime is 21023545321. The next prime is 21023545451. The reversal of 21023545421 is 12454532012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20836922500 + 186622921 = 144350^2 + 13661^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21023545421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21023545451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10511772710 + 10511772711.

It is an arithmetic number, because the mean of its divisors is an integer number (10511772711).

Almost surely, 2^21023545421 is an apocalyptic number.

It is an amenable number.

21023545421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21023545421 is an equidigital number, since it uses as much as digits as its factorization.

21023545421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9600, while the sum is 29.

The spelling of 21023545421 in words is "twenty-one billion, twenty-three million, five hundred forty-five thousand, four hundred twenty-one".