7561 has 2 divisors, whose sum is σ = 7562. Its totient is φ = 7560.
The previous prime is 7559. The next prime is 7573. The reversal of 7561 is 1657.
It is the 36-th star number.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 5625 + 1936 = 75^2 + 44^2 .
It is an emirp because it is prime and its reverse (1657) is a distict prime.
It is a cyclic number.
It is not a de Polignac number, because 7561 - 21 = 7559 is a prime.
Together with 7559, it forms a pair of twin primes.
It is a Chen prime.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (7541) by changing a digit.
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 as a sum of consecutive naturals, namely, 3780 + 3781.
It is an arithmetic number, because the mean of its divisors is an integer number (3781).
27561 is an apocalyptic number.
It is an amenable number.
7561 is a deficient number, since it is larger than the sum of its proper divisors (1).
7561 is an equidigital number, since it uses as much as digits as its factorization.
7561 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 210, while the sum is 19.
The square root of 7561 is about 86.9540108333. The cubic root of 7561 is about 19.6272631844.
It can be divided in two parts, 756 and 1, that added together give a palindrome (757).
The spelling of 7561 in words is "seven thousand, five hundred sixty-one".
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