20805680 has 80 divisors (see below), whose sum is σ = 56407104. Its totient is φ = 6988800.

The previous prime is 20805647. The next prime is 20805689. The reversal of 20805680 is 8650802.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (20805689) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29330 + ... + 30030.

Almost surely, 2^20805680 is an apocalyptic number.

20805680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20805680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28203552).

20805680 is an abundant number, since it is smaller than the sum of its proper divisors (35601424).

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

20805680 is a wasteful number, since it uses less digits than its factorization.

20805680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 774 (or 768 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 20805680 is about 4561.3243690840. The cubic root of 20805680 is about 275.0388044415.

The spelling of 20805680 in words is "twenty million, eight hundred five thousand, six hundred eighty".