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20321280 = 21034572

20321280 has 330 divisors, whose sum is σ = 84708954. Its totient is φ = 4644864.

The previous prime is 20321269. The next prime is 20321293. The reversal of 20321280 is 8212302.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 16257024 + 4064256 = 4032^2 + 2016^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 2903037 + ... + 2903043.

Almost surely, 220321280 is an apocalyptic number.

20321280 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 20321280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42354477).

20321280 is an abundant number, since it is smaller than the sum of its proper divisors (64387674).

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

20321280 is an equidigital number, since it uses as much as digits as its factorization.

20321280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51 (or 17 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 20321280 is about 4507.9130426396. The cubic root of 20321280 is about 272.8875276337.

Adding to 20321280 its reverse (8212302), we get a palindrome (28533582).

The spelling of 20321280 in words is "twenty million, three hundred twenty-one thousand, two hundred eighty".