20821680 has 180 divisors, whose sum is σ = 77182560. Its totient is φ = 5026560.

The previous prime is 20821667. The next prime is 20821709. The reversal of 20821680 is 8612802.

It is a tau number, because it is divible by the number of its divisors (180).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 87001 + ... + 87239.

It is an arithmetic number, because the mean of its divisors is an integer number (428792).

Almost surely, 2^20821680 is an apocalyptic number.

20821680 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 20821680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38591280).

20821680 is an abundant number, since it is smaller than the sum of its proper divisors (56360880).

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

20821680 is a wasteful number, since it uses less digits than its factorization.

20821680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280 (or 260 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 20821680 is about 4563.0779086051. The cubic root of 20821680 is about 275.1092898938.

The spelling of 20821680 in words is "twenty million, eight hundred twenty-one thousand, six hundred eighty".