20517680 has 20 divisors (see below), whose sum is σ = 47703792. Its totient is φ = 8207040.

The previous prime is 20517677. The next prime is 20517719. The reversal of 20517680 is 8671502.

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 128156 + ... + 128315.

Almost surely, 2^20517680 is an apocalyptic number.

20517680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20517680 is an abundant number, since it is smaller than the sum of its proper divisors (27186112).

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

20517680 is a wasteful number, since it uses less digits than its factorization.

20517680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256484 (or 256478 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 20517680 is about 4529.6445776683. The cubic root of 20517680 is about 273.7638400598.

The spelling of 20517680 in words is "twenty million, five hundred seventeen thousand, six hundred eighty".