61561 has 2 divisors, whose sum is σ = 61562. Its totient is φ = 61560.

The previous prime is 61559. The next prime is 61583. The reversal of 61561 is 16516.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 59536 + 2025 = 244^2 + 45^2 .

It is a cyclic number.

It is not a de Polignac number, because 61561 - 2¹ = 61559 is a prime.

Together with 61559, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (61511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30780 + 30781.

It is an arithmetic number, because the mean of its divisors is an integer number (30781).

2⁶¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

61561 is a deficient number, since it is larger than the sum of its proper divisors (1).

61561 is an equidigital number, since it uses as much as digits as its factorization.

61561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 180, while the sum is 19.

The square root of 61561 is about 248.1148927412. The cubic root of 61561 is about 39.4852799929.

It can be divided in two parts, 615 and 61, that added together give a palindrome (676).

The spelling of 61561 in words is "sixty-one thousand, five hundred sixty-one".