20643984 has 100 divisors (see below), whose sum is σ = 63331884. Its totient is φ = 6469632.

The previous prime is 20643947. The next prime is 20644003. The reversal of 20643984 is 48934602.

It is a happy number.

20643984 is a `hidden beast` number, since 2 + 0 + 643 + 9 + 8 + 4 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 7683984 + 12960000 = 2772^2 + 3600^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 21564 + ... + 22500.

Almost surely, 2^20643984 is an apocalyptic number.

20643984 is a gapful number since it is divisible by the number (24) 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 20643984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31665942).

20643984 is an abundant number, since it is smaller than the sum of its proper divisors (42687900).

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

20643984 is a wasteful number, since it uses less digits than its factorization.

20643984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 974 (or 959 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 20643984 is about 4543.5651200351. The cubic root of 20643984 is about 274.3244420762.

The spelling of 20643984 in words is "twenty million, six hundred forty-three thousand, nine hundred eighty-four".