20688661 has 24 divisors (see below), whose sum is σ = 25553024. Its totient is φ = 16394400.

The previous prime is 20688659. The next prime is 20688667. The reversal of 20688661 is 16688602.

It is not a de Polignac number, because 20688661 - 2¹ = 20688659 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a self number, because there is not a number n which added to its sum of digits gives 20688661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20688667) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 136936 + ... + 137086.

Almost surely, 2^20688661 is an apocalyptic number.

It is an amenable number.

20688661 is a deficient number, since it is larger than the sum of its proper divisors (4864363).

20688661 is a wasteful number, since it uses less digits than its factorization.

20688661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241 (or 218 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 20688661 is about 4548.4789765371. The cubic root of 20688661 is about 274.5221939956.

20688661 divided by its sum of digits (37) gives a triangular number (559153 = T₁₀₅₇).

The spelling of 20688661 in words is "twenty million, six hundred eighty-eight thousand, six hundred sixty-one".