20645856 has 288 divisors, whose sum is σ = 78624000. Its totient is φ = 5080320.

The previous prime is 20645843. The next prime is 20645857. The reversal of 20645856 is 65854602.

20645856 is a `hidden beast` number, since 2 + 0 + 645 + 8 + 5 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 20645856.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20645857) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1086615 + ... + 1086633.

It is an arithmetic number, because the mean of its divisors is an integer number (273000).

Almost surely, 2^20645856 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20645856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39312000).

20645856 is an abundant number, since it is smaller than the sum of its proper divisors (57978144).

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

20645856 is a wasteful number, since it uses less digits than its factorization.

20645856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67 (or 42 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

The square root of 20645856 is about 4543.7711209963. The cubic root of 20645856 is about 274.3327337547.

The spelling of 20645856 in words is "twenty million, six hundred forty-five thousand, eight hundred fifty-six".