1643683961 has 2 divisors, whose sum is σ = 1643683962. Its totient is φ = 1643683960.

The previous prime is 1643683919. The next prime is 1643683969. The reversal of 1643683961 is 1693863461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1636687936 + 6996025 = 40456^2 + 2645^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643683961 - 2⁶ = 1643683897 is a prime.

It is not a weakly prime, because it can be changed into another prime (1643683969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 821841980 + 821841981.

It is an arithmetic number, because the mean of its divisors is an integer number (821841981).

Almost surely, 2^1643683961 is an apocalyptic number.

It is an amenable number.

1643683961 is a deficient number, since it is larger than the sum of its proper divisors (1).

1643683961 is an equidigital number, since it uses as much as digits as its factorization.

1643683961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 559872, while the sum is 47.

The square root of 1643683961 is about 40542.3724145492. The cubic root of 1643683961 is about 1180.1560554404.

The spelling of 1643683961 in words is "one billion, six hundred forty-three million, six hundred eighty-three thousand, nine hundred sixty-one".