21431642261 has 2 divisors, whose sum is σ = 21431642262. Its totient is φ = 21431642260.

The previous prime is 21431642179. The next prime is 21431642327. The reversal of 21431642261 is 16224613412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15748744036 + 5682898225 = 125494^2 + 75385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21431642261 - 2²⁶ = 21364533397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21431642761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715821130 + 10715821131.

It is an arithmetic number, because the mean of its divisors is an integer number (10715821131).

Almost surely, 2^21431642261 is an apocalyptic number.

It is an amenable number.

21431642261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431642261 is an equidigital number, since it uses as much as digits as its factorization.

21431642261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 32.

The spelling of 21431642261 in words is "twenty-one billion, four hundred thirty-one million, six hundred forty-two thousand, two hundred sixty-one".