1961 has 4 divisors (see below), whose sum is σ = 2052. Its totient is φ = 1872.
The previous prime is 1951. The next prime is 1973. The reversal of 1961 is 1691.
1961 is nontrivially palindromic in base 13.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1691 = 19 ⋅89.
It can be written as a sum of positive squares in 2 ways, for example, as 1600 + 361 = 40^2 + 19^2 .
It is a cyclic number.
It is not a de Polignac number, because 1961 - 210 = 937 is a prime.
1961 is a strobogrammatic number because it is the same when read upside-down.
It is a Duffinian number.
1961 is an undulating number in base 13.
It is a Curzon number.
It is a plaindrome in base 15.
It is not an unprimeable number, because it can be changed into a prime (1901) 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 in 3 ways as a sum of consecutive naturals, for example, 11 + ... + 63.
It is an arithmetic number, because the mean of its divisors is an integer number (513).
It is an amenable number.
1961 is a deficient number, since it is larger than the sum of its proper divisors (91).
1961 is an equidigital number, since it uses as much as digits as its factorization.
1961 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 90.
The product of its digits is 54, while the sum is 17.
The square root of 1961 is about 44.2831796510. The cubic root of 1961 is about 12.5167774712.
The spelling of 1961 in words is "one thousand, nine hundred sixty-one".
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