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21940 = 2251097
BaseRepresentation
bin101010110110100
31010002121
411112310
51200230
6245324
7120652
oct52664
933077
1021940
1115536
1210844
139ca9
147dd2
15677a
hex55b4

21940 has 12 divisors (see below), whose sum is σ = 46116. Its totient is φ = 8768.

The previous prime is 21937. The next prime is 21943. The reversal of 21940 is 4912.

21940 = 312 + 322 + ... + 452.

It is an interprime number because it is at equal distance from previous prime (21937) and next prime (21943).

It can be written as a sum of positive squares in 2 ways, for example, as 7056 + 14884 = 84^2 + 122^2 .

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 529 + ... + 568.

It is an arithmetic number, because the mean of its divisors is an integer number (3843).

221940 is an apocalyptic number.

21940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21940 is an abundant number, since it is smaller than the sum of its proper divisors (24176).

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 (23058).

21940 is a wasteful number, since it uses less digits than its factorization.

21940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1106 (or 1104 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21940 is about 148.1215716903. The cubic root of 21940 is about 27.9948970292.

It can be divided in two parts, 21 and 940, that added together give a square (961 = 312).

The spelling of 21940 in words is "twenty-one thousand, nine hundred forty".

Divisors: 1 2 4 5 10 20 1097 2194 4388 5485 10970 21940