81897617 has 2 divisors, whose sum is σ = 81897618. Its totient is φ = 81897616.

The previous prime is 81897611. The next prime is 81897661. The reversal of 81897617 is 71679818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72063121 + 9834496 = 8489^2 + 3136^2 .

It is a cyclic number.

It is not a de Polignac number, because 81897617 - 2¹² = 81893521 is a prime.

It is not a weakly prime, because it can be changed into another prime (81897611) 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, 40948808 + 40948809.

It is an arithmetic number, because the mean of its divisors is an integer number (40948809).

Almost surely, 2^81897617 is an apocalyptic number.

It is an amenable number.

81897617 is a deficient number, since it is larger than the sum of its proper divisors (1).

81897617 is an equidigital number, since it uses as much as digits as its factorization.

81897617 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 169344, while the sum is 47.

The square root of 81897617 is about 9049.7302169733. The cubic root of 81897617 is about 434.2672598376.

The spelling of 81897617 in words is "eighty-one million, eight hundred ninety-seven thousand, six hundred seventeen".