20644560 has 120 divisors (see below), whose sum is σ = 70770024. Its totient is φ = 5391360.

The previous prime is 20644537. The next prime is 20644627. The reversal of 20644560 is 6544602.

20644560 = T₈₅₆ + T₈₅₇ + ... + T₉₀₈.

It is a happy number.

20644560 is a `hidden beast` number, since 206 + 4 + 456 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 2903616 + 17740944 = 1704^2 + 4212^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a congruent number.

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, 37890 + ... + 38430.

Almost surely, 2^20644560 is an apocalyptic number.

20644560 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 20644560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35385012).

20644560 is an abundant number, since it is smaller than the sum of its proper divisors (50125464).

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

20644560 is a wasteful number, since it uses less digits than its factorization.

20644560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 613 (or 604 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 20644560 is about 4543.6285059410. The cubic root of 20644560 is about 274.3269934153.

The spelling of 20644560 in words is "twenty million, six hundred forty-four thousand, five hundred sixty".