840393661 has 2 divisors, whose sum is σ = 840393662. Its totient is φ = 840393660.

The previous prime is 840393647. The next prime is 840393707. The reversal of 840393661 is 166393048.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 744471225 + 95922436 = 27285^2 + 9794^2 .

It is a cyclic number.

It is not a de Polignac number, because 840393661 - 2²¹ = 838296509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (840393611) 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, 420196830 + 420196831.

It is an arithmetic number, because the mean of its divisors is an integer number (420196831).

Almost surely, 2^840393661 is an apocalyptic number.

It is an amenable number.

840393661 is a deficient number, since it is larger than the sum of its proper divisors (1).

840393661 is an equidigital number, since it uses as much as digits as its factorization.

840393661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 93312, while the sum is 40.

The square root of 840393661 is about 28989.5439943439. The cubic root of 840393661 is about 943.6861676576.

The spelling of 840393661 in words is "eight hundred forty million, three hundred ninety-three thousand, six hundred sixty-one".