61981 has 2 divisors, whose sum is σ = 61982. Its totient is φ = 61980.

The previous prime is 61979. The next prime is 61987. The reversal of 61981 is 18916.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54756 + 7225 = 234^2 + 85^2 .

It is a cyclic number.

It is not a de Polignac number, because 61981 - 2¹ = 61979 is a prime.

It is a super-2 number, since 2×61981² = 7683288722, which contains 22 as substring.

Together with 61979, it forms a pair of twin primes.

It is a plaindrome in base 13.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30990 + 30991.

It is an arithmetic number, because the mean of its divisors is an integer number (30991).

2⁶¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

61981 is a deficient number, since it is larger than the sum of its proper divisors (1).

61981 is an equidigital number, since it uses as much as digits as its factorization.

61981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 25.

The square root of 61981 is about 248.9598361182. The cubic root of 61981 is about 39.5748726762.

The spelling of 61981 in words is "sixty-one thousand, nine hundred eighty-one".