210540721 has 2 divisors, whose sum is σ = 210540722. Its totient is φ = 210540720.

The previous prime is 210540719. The next prime is 210540739. The reversal of 210540721 is 127045012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 150307600 + 60233121 = 12260^2 + 7761^2 .

It is a cyclic number.

It is not a de Polignac number, because 210540721 - 2¹ = 210540719 is a prime.

Together with 210540719, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 210540692 and 210540701.

It is not a weakly prime, because it can be changed into another prime (210540791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105270360 + 105270361.

It is an arithmetic number, because the mean of its divisors is an integer number (105270361).

Almost surely, 2^210540721 is an apocalyptic number.

It is an amenable number.

210540721 is a deficient number, since it is larger than the sum of its proper divisors (1).

210540721 is an equidigital number, since it uses as much as digits as its factorization.

210540721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 210540721 is about 14510.0213990194. The cubic root of 210540721 is about 594.9019173117.

Adding to 210540721 its reverse (127045012), we get a palindrome (337585733).

The spelling of 210540721 in words is "two hundred ten million, five hundred forty thousand, seven hundred twenty-one".