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20640000 = 2835443
BaseRepresentation
bin100111010111…
…1000100000000
31102211121202110
41032233010000
520240440000
62014215320
7340302633
oct116570400
942747673
1020640000
1110718157
126ab4540
134378824
142a53c1a
151c2a850
hex13af100

20640000 has 180 divisors, whose sum is σ = 70240016. Its totient is φ = 5376000.

The previous prime is 20639959. The next prime is 20640001. The reversal of 20640000 is 4602.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is not an unprimeable number, because it can be changed into a prime (20640001) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 479979 + ... + 480021.

Almost surely, 220640000 is an apocalyptic number.

20640000 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 20640000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35120008).

20640000 is an abundant number, since it is smaller than the sum of its proper divisors (49600016).

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

20640000 is an frugal number, since it uses more digits than its factorization.

20640000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 53 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 20640000 is about 4543.1266766402. The cubic root of 20640000 is about 274.3067940148.

Adding to 20640000 its reverse (4602), we get a palindrome (20644602).

The spelling of 20640000 in words is "twenty million, six hundred forty thousand".