81661739 has 2 divisors, whose sum is σ = 81661740. Its totient is φ = 81661738.

The previous prime is 81661733. The next prime is 81661751. The reversal of 81661739 is 93716618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81661739 - 2⁸ = 81661483 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81661696 and 81661705.

It is not a weakly prime, because it can be changed into another prime (81661733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40830869 + 40830870.

It is an arithmetic number, because the mean of its divisors is an integer number (40830870).

Almost surely, 2^81661739 is an apocalyptic number.

81661739 is a deficient number, since it is larger than the sum of its proper divisors (1).

81661739 is an equidigital number, since it uses as much as digits as its factorization.

81661739 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432, while the sum is 41.

The square root of 81661739 is about 9036.6884974530. The cubic root of 81661739 is about 433.8499396264.

The spelling of 81661739 in words is "eighty-one million, six hundred sixty-one thousand, seven hundred thirty-nine".