81749839 has 2 divisors, whose sum is σ = 81749840. Its totient is φ = 81749838.

The previous prime is 81749831. The next prime is 81749867. The reversal of 81749839 is 93894718.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81749839 - 2³ = 81749831 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81749792 and 81749801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81749831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40874919 + 40874920.

It is an arithmetic number, because the mean of its divisors is an integer number (40874920).

Almost surely, 2^81749839 is an apocalyptic number.

81749839 is a deficient number, since it is larger than the sum of its proper divisors (1).

81749839 is an equidigital number, since it uses as much as digits as its factorization.

81749839 is an evil number, because the sum of its binary digits is even.

The product of its digits is 435456, while the sum is 49.

The square root of 81749839 is about 9041.5617566878. The cubic root of 81749839 is about 434.0059018643.

The spelling of 81749839 in words is "eighty-one million, seven hundred forty-nine thousand, eight hundred thirty-nine".