21036253817 has 2 divisors, whose sum is σ = 21036253818. Its totient is φ = 21036253816.

The previous prime is 21036253793. The next prime is 21036253829. The reversal of 21036253817 is 71835263012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10753482601 + 10282771216 = 103699^2 + 101404^2 .

It is a cyclic number.

It is not a de Polignac number, because 21036253817 - 2¹² = 21036249721 is a prime.

It is not a weakly prime, because it can be changed into another prime (21036253877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10518126908 + 10518126909.

It is an arithmetic number, because the mean of its divisors is an integer number (10518126909).

Almost surely, 2^21036253817 is an apocalyptic number.

It is an amenable number.

21036253817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21036253817 is an equidigital number, since it uses as much as digits as its factorization.

21036253817 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 60480, while the sum is 38.

The spelling of 21036253817 in words is "twenty-one billion, thirty-six million, two hundred fifty-three thousand, eight hundred seventeen".