21105445421 has 2 divisors, whose sum is σ = 21105445422. Its totient is φ = 21105445420.

The previous prime is 21105445409. The next prime is 21105445433. The reversal of 21105445421 is 12454450112.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21105445409) and next prime (21105445433).

It can be written as a sum of positive squares in only one way, i.e., 19800429796 + 1305015625 = 140714^2 + 36125^2 .

It is a cyclic number.

It is not a de Polignac number, because 21105445421 - 2¹⁸ = 21105183277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21105445121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552722710 + 10552722711.

It is an arithmetic number, because the mean of its divisors is an integer number (10552722711).

Almost surely, 2^21105445421 is an apocalyptic number.

It is an amenable number.

21105445421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105445421 is an equidigital number, since it uses as much as digits as its factorization.

21105445421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6400, while the sum is 29.

Adding to 21105445421 its reverse (12454450112), we get a palindrome (33559895533).

The spelling of 21105445421 in words is "twenty-one billion, one hundred five million, four hundred forty-five thousand, four hundred twenty-one".