81562409 has 2 divisors, whose sum is σ = 81562410. Its totient is φ = 81562408.

The previous prime is 81562391. The next prime is 81562423. The reversal of 81562409 is 90426518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45225625 + 36336784 = 6725^2 + 6028^2 .

It is a cyclic number.

It is not a de Polignac number, because 81562409 - 2¹² = 81558313 is a prime.

It is not a weakly prime, because it can be changed into another prime (81562109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40781204 + 40781205.

It is an arithmetic number, because the mean of its divisors is an integer number (40781205).

Almost surely, 2^81562409 is an apocalyptic number.

It is an amenable number.

81562409 is a deficient number, since it is larger than the sum of its proper divisors (1).

81562409 is an equidigital number, since it uses as much as digits as its factorization.

81562409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 81562409 is about 9031.1908960004. The cubic root of 81562409 is about 433.6739624814.

The spelling of 81562409 in words is "eighty-one million, five hundred sixty-two thousand, four hundred nine".