20688657 has 8 divisors (see below), whose sum is σ = 30092640. Its totient is φ = 12538560.

The previous prime is 20688649. The next prime is 20688659. The reversal of 20688657 is 75688602.

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

It is not a de Polignac number, because 20688657 - 2³ = 20688649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20688659) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 313432 + ... + 313497.

It is an arithmetic number, because the mean of its divisors is an integer number (3761580).

Almost surely, 2^20688657 is an apocalyptic number.

It is an amenable number.

20688657 is a deficient number, since it is larger than the sum of its proper divisors (9403983).

20688657 is a wasteful number, since it uses less digits than its factorization.

20688657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 626943.

The product of its (nonzero) digits is 161280, while the sum is 42.

The square root of 20688657 is about 4548.4785368297. The cubic root of 20688657 is about 274.5221763033.

Subtracting 20688657 from its reverse (75688602), we obtain a palindrome (54999945).

The spelling of 20688657 in words is "twenty million, six hundred eighty-eight thousand, six hundred fifty-seven".