642733661 has 2 divisors, whose sum is σ = 642733662. Its totient is φ = 642733660.

The previous prime is 642733639. The next prime is 642733687. The reversal of 642733661 is 166337246.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 548449561 + 94284100 = 23419^2 + 9710^2 .

It is a cyclic number.

It is not a de Polignac number, because 642733661 - 2¹⁰ = 642732637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642733631) 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, 321366830 + 321366831.

It is an arithmetic number, because the mean of its divisors is an integer number (321366831).

Almost surely, 2^642733661 is an apocalyptic number.

It is an amenable number.

642733661 is a deficient number, since it is larger than the sum of its proper divisors (1).

642733661 is an equidigital number, since it uses as much as digits as its factorization.

642733661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 38.

The square root of 642733661 is about 25352.1924298472. The cubic root of 642733661 is about 862.9991111329. Note that the first 3 decimals are identical.

The spelling of 642733661 in words is "six hundred forty-two million, seven hundred thirty-three thousand, six hundred sixty-one".