1688638505 has 8 divisors (see below), whose sum is σ = 2075790024. Its totient is φ = 1317961600.

The previous prime is 1688638489. The next prime is 1688638507. The reversal of 1688638505 is 5058368861.

It can be written as a sum of positive squares in 4 ways, for example, as 288082729 + 1400555776 = 16973^2 + 37424^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1688638505 - 2⁴ = 1688638489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1688638507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4118426 + ... + 4118835.

It is an arithmetic number, because the mean of its divisors is an integer number (259473753).

Almost surely, 2^1688638505 is an apocalyptic number.

It is an amenable number.

1688638505 is a deficient number, since it is larger than the sum of its proper divisors (387151519).

1688638505 is an equidigital number, since it uses as much as digits as its factorization.

1688638505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8237307.

The product of its (nonzero) digits is 1382400, while the sum is 50.

The square root of 1688638505 is about 41093.0469179398. The cubic root of 1688638505 is about 1190.8184716060.

The spelling of 1688638505 in words is "one billion, six hundred eighty-eight million, six hundred thirty-eight thousand, five hundred five".