21520237513 has 2 divisors, whose sum is σ = 21520237514. Its totient is φ = 21520237512.

The previous prime is 21520237489. The next prime is 21520237561. The reversal of 21520237513 is 31573202512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15647007744 + 5873229769 = 125088^2 + 76637^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520237513 - 2¹⁷ = 21520106441 is a prime.

It is not a weakly prime, because it can be changed into another prime (21520234513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760118756 + 10760118757.

It is an arithmetic number, because the mean of its divisors is an integer number (10760118757).

Almost surely, 2^21520237513 is an apocalyptic number.

It is an amenable number.

21520237513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520237513 is an equidigital number, since it uses as much as digits as its factorization.

21520237513 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12600, while the sum is 31.

The spelling of 21520237513 in words is "twenty-one billion, five hundred twenty million, two hundred thirty-seven thousand, five hundred thirteen".