81220609 has 2 divisors, whose sum is σ = 81220610. Its totient is φ = 81220608.

The previous prime is 81220591. The next prime is 81220627. The reversal of 81220609 is 90602218.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (81220591) and next prime (81220627).

It can be written as a sum of positive squares in only one way, i.e., 62489025 + 18731584 = 7905^2 + 4328^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81220609 is a prime.

It is not a weakly prime, because it can be changed into another prime (81220669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40610304 + 40610305.

It is an arithmetic number, because the mean of its divisors is an integer number (40610305).

Almost surely, 2^81220609 is an apocalyptic number.

It is an amenable number.

81220609 is a deficient number, since it is larger than the sum of its proper divisors (1).

81220609 is an equidigital number, since it uses as much as digits as its factorization.

81220609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 81220609 is about 9012.2477218505. The cubic root of 81220609 is about 433.0673214827.

The spelling of 81220609 in words is "eighty-one million, two hundred twenty thousand, six hundred nine".