210016721 has 2 divisors, whose sum is σ = 210016722. Its totient is φ = 210016720.

The previous prime is 210016649. The next prime is 210016733. The reversal of 210016721 is 127610012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 131446225 + 78570496 = 11465^2 + 8864^2 .

It is a cyclic number.

It is not a de Polignac number, because 210016721 - 2¹⁰ = 210015697 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 210016693 and 210016702.

It is not a weakly prime, because it can be changed into another prime (210016421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105008360 + 105008361.

It is an arithmetic number, because the mean of its divisors is an integer number (105008361).

Almost surely, 2^210016721 is an apocalyptic number.

It is an amenable number.

210016721 is a deficient number, since it is larger than the sum of its proper divisors (1).

210016721 is an equidigital number, since it uses as much as digits as its factorization.

210016721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 210016721 is about 14491.9536640165. The cubic root of 210016721 is about 594.4079707813.

Adding to 210016721 its reverse (127610012), we get a palindrome (337626733).

The spelling of 210016721 in words is "two hundred ten million, sixteen thousand, seven hundred twenty-one".