20688138 has 12 divisors (see below), whose sum is σ = 44824338. Its totient is φ = 6896040.

The previous prime is 20688121. The next prime is 20688197. The reversal of 20688138 is 83188602.

It can be written as a sum of positive squares in only one way, i.e., 14768649 + 5919489 = 3843^2 + 2433^2 .

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 574653 + ... + 574688.

Almost surely, 2^20688138 is an apocalyptic number.

20688138 is an abundant number, since it is smaller than the sum of its proper divisors (24136200).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20688138 is a wasteful number, since it uses less digits than its factorization.

20688138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1149349 (or 1149346 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 20688138 is about 4548.4214844273. The cubic root of 20688138 is about 274.5198807105.

The spelling of 20688138 in words is "twenty million, six hundred eighty-eight thousand, one hundred thirty-eight".