21135254321 has 2 divisors, whose sum is σ = 21135254322. Its totient is φ = 21135254320.

The previous prime is 21135254297. The next prime is 21135254339. The reversal of 21135254321 is 12345253112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18039444721 + 3095809600 = 134311^2 + 55640^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135254321 - 2²² = 21131060017 is a prime.

It is not a weakly prime, because it can be changed into another prime (21135254381) 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, 10567627160 + 10567627161.

It is an arithmetic number, because the mean of its divisors is an integer number (10567627161).

Almost surely, 2^21135254321 is an apocalyptic number.

It is an amenable number.

21135254321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135254321 is an equidigital number, since it uses as much as digits as its factorization.

21135254321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7200, while the sum is 29.

The spelling of 21135254321 in words is "twenty-one billion, one hundred thirty-five million, two hundred fifty-four thousand, three hundred twenty-one".