21726831421 has 2 divisors, whose sum is σ = 21726831422. Its totient is φ = 21726831420.

The previous prime is 21726831403. The next prime is 21726831437. The reversal of 21726831421 is 12413862712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17295932196 + 4430899225 = 131514^2 + 66565^2 .

It is a cyclic number.

It is not a de Polignac number, because 21726831421 - 2¹⁹ = 21726307133 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21726831491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10863415710 + 10863415711.

It is an arithmetic number, because the mean of its divisors is an integer number (10863415711).

Almost surely, 2^21726831421 is an apocalyptic number.

It is an amenable number.

21726831421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21726831421 is an equidigital number, since it uses as much as digits as its factorization.

21726831421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 37.

The spelling of 21726831421 in words is "twenty-one billion, seven hundred twenty-six million, eight hundred thirty-one thousand, four hundred twenty-one".