81690802261 has 2 divisors, whose sum is σ = 81690802262. Its totient is φ = 81690802260.

The previous prime is 81690802213. The next prime is 81690802283. The reversal of 81690802261 is 16220809618.

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., 80375652036 + 1315150225 = 283506^2 + 36265^2 .

It is a cyclic number.

It is not a de Polignac number, because 81690802261 - 2⁹ = 81690801749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81690802961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40845401130 + 40845401131.

It is an arithmetic number, because the mean of its divisors is an integer number (40845401131).

Almost surely, 2^81690802261 is an apocalyptic number.

It is an amenable number.

81690802261 is a deficient number, since it is larger than the sum of its proper divisors (1).

81690802261 is an equidigital number, since it uses as much as digits as its factorization.

81690802261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 82944, while the sum is 43.

The spelling of 81690802261 in words is "eighty-one billion, six hundred ninety million, eight hundred two thousand, two hundred sixty-one".