1643073721 has 2 divisors, whose sum is σ = 1643073722. Its totient is φ = 1643073720.

The previous prime is 1643073671. The next prime is 1643073769. The reversal of 1643073721 is 1273703461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1483405225 + 159668496 = 38515^2 + 12636^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643073721 - 2²⁹ = 1106202809 is a prime.

It is not a weakly prime, because it can be changed into another prime (1643073121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821536860 + 821536861.

It is an arithmetic number, because the mean of its divisors is an integer number (821536861).

Almost surely, 2^1643073721 is an apocalyptic number.

It is an amenable number.

1643073721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643073721 is an equidigital number, since it uses as much as digits as its factorization.

1643073721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21168, while the sum is 34.

The square root of 1643073721 is about 40534.8457626275. The cubic root of 1643073721 is about 1180.0099877063.

The spelling of 1643073721 in words is "one billion, six hundred forty-three million, seventy-three thousand, seven hundred twenty-one".