81700609 has 2 divisors, whose sum is σ = 81700610. Its totient is φ = 81700608.

The previous prime is 81700607. The next prime is 81700621. The reversal of 81700609 is 90600718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54169600 + 27531009 = 7360^2 + 5247^2 .

It is a cyclic number.

It is not a de Polignac number, because 81700609 - 2¹ = 81700607 is a prime.

Together with 81700607, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81700601) 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, 40850304 + 40850305.

It is an arithmetic number, because the mean of its divisors is an integer number (40850305).

Almost surely, 2^81700609 is an apocalyptic number.

It is an amenable number.

81700609 is a deficient number, since it is larger than the sum of its proper divisors (1).

81700609 is an equidigital number, since it uses as much as digits as its factorization.

81700609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 81700609 is about 9038.8389187993. The cubic root of 81700609 is about 433.9187644821.

It can be divided in two parts, 81700 and 609, that multiplied together give a triangular number (49755300 = T₉₉₇₅).

The spelling of 81700609 in words is "eighty-one million, seven hundred thousand, six hundred nine".