216531521 has 2 divisors, whose sum is σ = 216531522. Its totient is φ = 216531520.

The previous prime is 216531509. The next prime is 216531529. The reversal of 216531521 is 125135612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 140754496 + 75777025 = 11864^2 + 8705^2 .

It is a cyclic number.

It is not a de Polignac number, because 216531521 - 2⁶ = 216531457 is a prime.

It is not a weakly prime, because it can be changed into another prime (216531529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108265760 + 108265761.

It is an arithmetic number, because the mean of its divisors is an integer number (108265761).

Almost surely, 2^216531521 is an apocalyptic number.

It is an amenable number.

216531521 is a deficient number, since it is larger than the sum of its proper divisors (1).

216531521 is an equidigital number, since it uses as much as digits as its factorization.

216531521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1800, while the sum is 26.

The square root of 216531521 is about 14715.0100577607. The cubic root of 216531521 is about 600.4917459405.

The spelling of 216531521 in words is "two hundred sixteen million, five hundred thirty-one thousand, five hundred twenty-one".