81739399 has 12 divisors (see below), whose sum is σ = 95237424. Its totient is φ = 69949824.

The previous prime is 81739393. The next prime is 81739433. The reversal of 81739399 is 99393718.

81739399 = T₁₈₀₂ + T₁₈₀₃ + ... + T₁₈₅₀.

It is not a de Polignac number, because 81739399 - 2⁷ = 81739271 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81739393) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 47319 + ... + 49015.

It is an arithmetic number, because the mean of its divisors is an integer number (7936452).

Almost surely, 2^81739399 is an apocalyptic number.

81739399 is a deficient number, since it is larger than the sum of its proper divisors (13498025).

81739399 is a wasteful number, since it uses less digits than its factorization.

81739399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2694 (or 2687 counting only the distinct ones).

The product of its digits is 367416, while the sum is 49.

The square root of 81739399 is about 9040.9844043666. The cubic root of 81739399 is about 433.9874259278.

The spelling of 81739399 in words is "eighty-one million, seven hundred thirty-nine thousand, three hundred ninety-nine".