21135815969 has 2 divisors, whose sum is σ = 21135815970. Its totient is φ = 21135815968.

The previous prime is 21135815959. The next prime is 21135816001. The reversal of 21135815969 is 96951853112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10694041744 + 10441774225 = 103412^2 + 102185^2 .

It is a cyclic number.

It is not a de Polignac number, because 21135815969 - 2⁸ = 21135815713 is a prime.

It is a super-2 number, since 2×21135815969² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21135815959) 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, 10567907984 + 10567907985.

It is an arithmetic number, because the mean of its divisors is an integer number (10567907985).

Almost surely, 2^21135815969 is an apocalyptic number.

It is an amenable number.

21135815969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135815969 is an equidigital number, since it uses as much as digits as its factorization.

21135815969 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 583200, while the sum is 50.

The spelling of 21135815969 in words is "twenty-one billion, one hundred thirty-five million, eight hundred fifteen thousand, nine hundred sixty-nine".