21253213065509 has 2 divisors, whose sum is σ = 21253213065510. Its totient is φ = 21253213065508.

The previous prime is 21253213065499. The next prime is 21253213065613. The reversal of 21253213065509 is 90556031235212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20196233736484 + 1056979329025 = 4494022^2 + 1028095^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253213065509 - 2⁴ = 21253213065493 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21253213065509.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21253213005509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10626606532754 + 10626606532755.

It is an arithmetic number, because the mean of its divisors is an integer number (10626606532755).

Almost surely, 2^{21253213065509} is an apocalyptic number.

It is an amenable number.

21253213065509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21253213065509 is an equidigital number, since it uses as much as digits as its factorization.

21253213065509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486000, while the sum is 44.

The spelling of 21253213065509 in words is "twenty-one trillion, two hundred fifty-three billion, two hundred thirteen million, sixty-five thousand, five hundred nine".