1861 has 2 divisors, whose sum is σ = 1862.
Its totient is φ = 1860.
The previous prime is 1847. The next prime is 1867. The reversal of 1861 is 1681.
1861 = 302 + 312.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 961 + 900 = 31^2 + 30^2
It is a cyclic number.
It is not a de Polignac number, because 1861 - 27 = 1733 is a prime.
It is a nialpdrome in base 15.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (1867) by changing a digit.
It is a good prime.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 930 + 931.
It is an arithmetic number, because the mean of its divisors is an integer number (931).
1861 is the 31-st centered square number.
It is an amenable number.
1861 is a deficient number, since it is larger than the sum of its proper divisors (1).
1861 is an equidigital number, since it uses as much as digits as its factorization.
1861 is an evil number, because the sum of its binary digits is even.
The product of its digits is 48, while the sum is 16.
The square root of 1861 is about 43.1393092202.
The cubic root of 1861 is about 12.3002930285.
The spelling of 1861 in words is "one thousand, eight hundred sixty-one".