816721729 has 2 divisors, whose sum is σ = 816721730. Its totient is φ = 816721728.

The previous prime is 816721721. The next prime is 816721739. The reversal of 816721729 is 927127618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 460531600 + 356190129 = 21460^2 + 18873^2 .

It is a cyclic number.

It is not a de Polignac number, because 816721729 - 2³ = 816721721 is a prime.

It is not a weakly prime, because it can be changed into another prime (816721721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408360864 + 408360865.

It is an arithmetic number, because the mean of its divisors is an integer number (408360865).

Almost surely, 2^816721729 is an apocalyptic number.

It is an amenable number.

816721729 is a deficient number, since it is larger than the sum of its proper divisors (1).

816721729 is an equidigital number, since it uses as much as digits as its factorization.

816721729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84672, while the sum is 43.

The square root of 816721729 is about 28578.3437063802. The cubic root of 816721729 is about 934.7411673571.

The spelling of 816721729 in words is "eight hundred sixteen million, seven hundred twenty-one thousand, seven hundred twenty-nine".