849561721 has 2 divisors, whose sum is σ = 849561722. Its totient is φ = 849561720.

The previous prime is 849561719. The next prime is 849561733. The reversal of 849561721 is 127165948.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 492351721 + 357210000 = 22189^2 + 18900^2 .

It is a cyclic number.

It is not a de Polignac number, because 849561721 - 2¹ = 849561719 is a prime.

Together with 849561719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (849561781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 424780860 + 424780861.

It is an arithmetic number, because the mean of its divisors is an integer number (424780861).

Almost surely, 2^849561721 is an apocalyptic number.

It is an amenable number.

849561721 is a deficient number, since it is larger than the sum of its proper divisors (1).

849561721 is an equidigital number, since it uses as much as digits as its factorization.

849561721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 120960, while the sum is 43.

The square root of 849561721 is about 29147.2420822280. The cubic root of 849561721 is about 947.1053983025.

The spelling of 849561721 in words is "eight hundred forty-nine million, five hundred sixty-one thousand, seven hundred twenty-one".