81243961 has 2 divisors, whose sum is σ = 81243962. Its totient is φ = 81243960.

The previous prime is 81243959. The next prime is 81243977. The reversal of 81243961 is 16934218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80281600 + 962361 = 8960^2 + 981^2 .

It is a cyclic number.

It is not a de Polignac number, because 81243961 - 2¹ = 81243959 is a prime.

Together with 81243959, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81243941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40621980 + 40621981.

It is an arithmetic number, because the mean of its divisors is an integer number (40621981).

Almost surely, 2^81243961 is an apocalyptic number.

It is an amenable number.

81243961 is a deficient number, since it is larger than the sum of its proper divisors (1).

81243961 is an equidigital number, since it uses as much as digits as its factorization.

81243961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 34.

The square root of 81243961 is about 9013.5431989867. The cubic root of 81243961 is about 433.1088217011.

The spelling of 81243961 in words is "eighty-one million, two hundred forty-three thousand, nine hundred sixty-one".