21431508809 has 2 divisors, whose sum is σ = 21431508810. Its totient is φ = 21431508808.

The previous prime is 21431508799. The next prime is 21431508821. The reversal of 21431508809 is 90880513412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21421249600 + 10259209 = 146360^2 + 3203^2 .

It is a cyclic number.

It is not a de Polignac number, because 21431508809 - 2¹² = 21431504713 is a prime.

It is not a weakly prime, because it can be changed into another prime (21431508829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715754404 + 10715754405.

It is an arithmetic number, because the mean of its divisors is an integer number (10715754405).

Almost surely, 2^21431508809 is an apocalyptic number.

It is an amenable number.

21431508809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431508809 is an equidigital number, since it uses as much as digits as its factorization.

21431508809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69120, while the sum is 41.

The spelling of 21431508809 in words is "twenty-one billion, four hundred thirty-one million, five hundred eight thousand, eight hundred nine".