1688720842 has 4 divisors (see below), whose sum is σ = 2533081266. Its totient is φ = 844360420.

The previous prime is 1688720819. The next prime is 1688720843. The reversal of 1688720842 is 2480278861.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 2480278861 = 523 ⋅4742407.

It can be written as a sum of positive squares in only one way, i.e., 1627396281 + 61324561 = 40341^2 + 7831^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1688720792 and 1688720801.

It is not an unprimeable number, because it can be changed into a prime (1688720843) 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, 422180209 + ... + 422180212.

Almost surely, 2^1688720842 is an apocalyptic number.

1688720842 is a deficient number, since it is larger than the sum of its proper divisors (844360424).

1688720842 is an equidigital number, since it uses as much as digits as its factorization.

1688720842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844360423.

The product of its (nonzero) digits is 344064, while the sum is 46.

The square root of 1688720842 is about 41094.0487418799. The cubic root of 1688720842 is about 1190.8378258228.

The spelling of 1688720842 in words is "one billion, six hundred eighty-eight million, seven hundred twenty thousand, eight hundred forty-two".