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21851 is a prime number
BaseRepresentation
bin101010101011011
31002222022
411111123
51144401
6245055
7120464
oct52533
932868
1021851
1115465
121078b
139c3b
147d6b
15671b
hex555b

21851 has 2 divisors, whose sum is σ = 21852. Its totient is φ = 21850.

The previous prime is 21841. The next prime is 21859. The reversal of 21851 is 15812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21851 - 26 = 21787 is a prime.

It is a plaindrome in base 4 and base 16.

It is not a weakly prime, because it can be changed into another prime (21859) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10925 + 10926.

It is an arithmetic number, because the mean of its divisors is an integer number (10926).

221851 is an apocalyptic number.

21851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21851 is an equidigital number, since it uses as much as digits as its factorization.

21851 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80, while the sum is 17.

The square root of 21851 is about 147.8208375027. The cubic root of 21851 is about 27.9569917960.

It can be divided in two parts, 21 and 851, that multiplied together give a palindrome (17871).

The spelling of 21851 in words is "twenty-one thousand, eight hundred fifty-one".