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21030 has 16 divisors (see below), whose sum is σ = 50544. Its totient is φ = 5600.

The previous prime is 21023. The next prime is 21031. The reversal of 21030 is 3012.

Adding to 21030 its reverse (3012), we get a palindrome (24042).

21030 = 712 + 722 + ... + 742.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 321 + ... + 380.

It is an arithmetic number, because the mean of its divisors is an integer number (3159).

221030 is an apocalyptic number.

21030 is an abundant number, since it is smaller than the sum of its proper divisors (29514).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25272).

21030 is a wasteful number, since it uses less digits than its factorization.

21030 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 711.

The product of its (nonzero) digits is 6, while the sum is 6.

The square root of 21030 is about 145.0172403544. The cubic root of 21030 is about 27.6023732469.

The spelling of 21030 in words is "twenty-one thousand, thirty".