816721739 has 2 divisors, whose sum is σ = 816721740. Its totient is φ = 816721738.

The previous prime is 816721729. The next prime is 816721771. The reversal of 816721739 is 937127618.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-816721739 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 816721739.

It is not a weakly prime, because it can be changed into another prime (816721729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408360869 + 408360870.

It is an arithmetic number, because the mean of its divisors is an integer number (408360870).

Almost surely, 2^816721739 is an apocalyptic number.

816721739 is a deficient number, since it is larger than the sum of its proper divisors (1).

816721739 is an equidigital number, since it uses as much as digits as its factorization.

816721739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 127008, while the sum is 44.

The square root of 816721739 is about 28578.3438813378. The cubic root of 816721739 is about 934.7411711721.

The spelling of 816721739 in words is "eight hundred sixteen million, seven hundred twenty-one thousand, seven hundred thirty-nine".