51581 has 2 divisors, whose sum is σ = 51582. Its totient is φ = 51580.
The previous prime is 51577. The next prime is 51593. The reversal of 51581 is 18515.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 27556 + 24025 = 166^2 + 155^2 .
It is a cyclic number.
It is not a de Polignac number, because 51581 - 22 = 51577 is a prime.
It is a super-2 number, since 2×515812 = 5321199122, which contains 22 as substring.
It is a Chen prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (51511) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25790 + 25791.
It is an arithmetic number, because the mean of its divisors is an integer number (25791).
251581 is an apocalyptic number.
It is an amenable number.
51581 is a deficient number, since it is larger than the sum of its proper divisors (1).
51581 is an equidigital number, since it uses as much as digits as its factorization.
51581 is an evil number, because the sum of its binary digits is even.
The product of its digits is 200, while the sum is 20.
The square root of 51581 is about 227.1145085634. The cubic root of 51581 is about 37.2245896698.
The spelling of 51581 in words is "fifty-one thousand, five hundred eighty-one".
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