20644820 has 48 divisors (see below), whose sum is σ = 49835520. Its totient is φ = 7037184.

The previous prime is 20644807. The next prime is 20644831. The reversal of 20644820 is 2844602.

It is a self number, because there is not a number n which added to its sum of digits gives 20644820.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33152 + ... + 33768.

It is an arithmetic number, because the mean of its divisors is an integer number (1038240).

Almost surely, 2^20644820 is an apocalyptic number.

20644820 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 20644820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24917760).

20644820 is an abundant number, since it is smaller than the sum of its proper divisors (29190700).

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

20644820 is a wasteful number, since it uses less digits than its factorization.

20644820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 872 (or 870 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 26.

The square root of 20644820 is about 4543.6571173450. The cubic root of 20644820 is about 274.3281450459.

The spelling of 20644820 in words is "twenty million, six hundred forty-four thousand, eight hundred twenty".