216747521 has 2 divisors, whose sum is σ = 216747522. Its totient is φ = 216747520.

The previous prime is 216747511. The next prime is 216747523. The reversal of 216747521 is 125747612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 211295296 + 5452225 = 14536^2 + 2335^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216747521 is a prime.

It is a Sophie Germain prime.

Together with 216747523, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (216747523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108373760 + 108373761.

It is an arithmetic number, because the mean of its divisors is an integer number (108373761).

Almost surely, 2^216747521 is an apocalyptic number.

It is an amenable number.

216747521 is a deficient number, since it is larger than the sum of its proper divisors (1).

216747521 is an equidigital number, since it uses as much as digits as its factorization.

216747521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23520, while the sum is 35.

The square root of 216747521 is about 14722.3476728408. The cubic root of 216747521 is about 600.6913521551.

Subtracting from 216747521 its reverse (125747612), we obtain a palindrome (90999909).

The spelling of 216747521 in words is "two hundred sixteen million, seven hundred forty-seven thousand, five hundred twenty-one".