81961961 has 2 divisors, whose sum is σ = 81961962. Its totient is φ = 81961960.

The previous prime is 81961927. The next prime is 81961967. The reversal of 81961961 is 16916918.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 56911936 + 25050025 = 7544^2 + 5005^2 .

It is a cyclic number.

It is not a de Polignac number, because 81961961 - 2⁶ = 81961897 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81961967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40980980 + 40980981.

It is an arithmetic number, because the mean of its divisors is an integer number (40980981).

Almost surely, 2^81961961 is an apocalyptic number.

It is an amenable number.

81961961 is a deficient number, since it is larger than the sum of its proper divisors (1).

81961961 is an equidigital number, since it uses as much as digits as its factorization.

81961961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23328, while the sum is 41.

The square root of 81961961 is about 9053.2845420875. The cubic root of 81961961 is about 434.3809594338.

The spelling of 81961961 in words is "eighty-one million, nine hundred sixty-one thousand, nine hundred sixty-one".