20708640 has 144 divisors (see below), whose sum is σ = 71999928. Its totient is φ = 5419008.

The previous prime is 20708599. The next prime is 20708663. The reversal of 20708640 is 4680702.

It can be written as a sum of positive squares in 4 ways, for example, as 20466576 + 242064 = 4524^2 + 492^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 105022 + ... + 105218.

Almost surely, 2^20708640 is an apocalyptic number.

20708640 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 20708640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35999964).

20708640 is an abundant number, since it is smaller than the sum of its proper divisors (51291288).

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

20708640 is a wasteful number, since it uses less digits than its factorization.

20708640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291 (or 280 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 20708640 is about 4550.6746752542. The cubic root of 20708640 is about 274.6105340827.

The spelling of 20708640 in words is "twenty million, seven hundred eight thousand, six hundred forty".