20911680 has 168 divisors, whose sum is σ = 73819512. Its totient is φ = 5431296.

The previous prime is 20911673. The next prime is 20911699. The reversal of 20911680 is 8611902.

It can be written as a sum of positive squares in 4 ways, for example, as 4460544 + 16451136 = 2112^2 + 4056^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 152572 + ... + 152708.

Almost surely, 2^20911680 is an apocalyptic number.

20911680 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 20911680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36909756).

20911680 is an abundant number, since it is smaller than the sum of its proper divisors (52907832).

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

20911680 is a wasteful number, since it uses less digits than its factorization.

20911680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213 (or 200 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 20911680 is about 4572.9290394669. The cubic root of 20911680 is about 275.5050992520.

The spelling of 20911680 in words is "twenty million, nine hundred eleven thousand, six hundred eighty".