20644000 has 96 divisors (see below), whose sum is σ = 54761616. Its totient is φ = 7603200.

The previous prime is 20643947. The next prime is 20644003. The reversal of 20644000 is 44602.

It can be written as a sum of positive squares in 8 ways, for example, as 104976 + 20539024 = 324^2 + 4532^2 .

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20644003) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51802 + ... + 52198.

Almost surely, 2^20644000 is an apocalyptic number.

20644000 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 20644000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27380808).

20644000 is an abundant number, since it is smaller than the sum of its proper divisors (34117616).

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

20644000 is a wasteful number, since it uses less digits than its factorization.

20644000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 435 (or 417 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 20644000 is about 4543.5668807667. The cubic root of 20644000 is about 274.3245129474.

Adding to 20644000 its reverse (44602), we get a palindrome (20688602).

The spelling of 20644000 in words is "twenty million, six hundred forty-four thousand".