21758238221 has 2 divisors, whose sum is σ = 21758238222. Its totient is φ = 21758238220.

The previous prime is 21758238197. The next prime is 21758238251. The reversal of 21758238221 is 12283285712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18086484196 + 3671754025 = 134486^2 + 60595^2 .

It is a cyclic number.

It is not a de Polignac number, because 21758238221 - 2³⁰ = 20684496397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21758238251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10879119110 + 10879119111.

It is an arithmetic number, because the mean of its divisors is an integer number (10879119111).

Almost surely, 2^21758238221 is an apocalyptic number.

It is an amenable number.

21758238221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21758238221 is an equidigital number, since it uses as much as digits as its factorization.

21758238221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 107520, while the sum is 41.

The spelling of 21758238221 in words is "twenty-one billion, seven hundred fifty-eight million, two hundred thirty-eight thousand, two hundred twenty-one".