20644400 has 120 divisors (see below), whose sum is σ = 58029024. Its totient is φ = 6912000.

The previous prime is 20644399. The next prime is 20644447. The reversal of 20644400 is 444602.

It is a Harshad number since it is a multiple of its sum of digits (20).

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, 204350 + ... + 204450.

Almost surely, 2^20644400 is an apocalyptic number.

20644400 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 20644400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29014512).

20644400 is an abundant number, since it is smaller than the sum of its proper divisors (37384624).

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

20644400 is a wasteful number, since it uses less digits than its factorization.

20644400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199 (or 188 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 20644400 is about 4543.6108988337. The cubic root of 20644400 is about 274.3262847147.

The spelling of 20644400 in words is "twenty million, six hundred forty-four thousand, four hundred".