21430751809 has 2 divisors, whose sum is σ = 21430751810. Its totient is φ = 21430751808.

The previous prime is 21430751777. The next prime is 21430751827. The reversal of 21430751809 is 90815703412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15493278784 + 5937473025 = 124472^2 + 77055^2 .

It is a cyclic number.

It is not a de Polignac number, because 21430751809 - 2⁵ = 21430751777 is a prime.

It is not a weakly prime, because it can be changed into another prime (21430751879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715375904 + 10715375905.

It is an arithmetic number, because the mean of its divisors is an integer number (10715375905).

Almost surely, 2^21430751809 is an apocalyptic number.

It is an amenable number.

21430751809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21430751809 is an equidigital number, since it uses as much as digits as its factorization.

21430751809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60480, while the sum is 40.

The spelling of 21430751809 in words is "twenty-one billion, four hundred thirty million, seven hundred fifty-one thousand, eight hundred nine".