81729814 has 4 divisors (see below), whose sum is σ = 122594724. Its totient is φ = 40864906.

The previous prime is 81729803. The next prime is 81729841. The reversal of 81729814 is 41892718.

81729814 = T₇₃₈₀ + T₇₃₈₁ + T₇₃₈₂.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20432452 + ... + 20432455.

It is an arithmetic number, because the mean of its divisors is an integer number (30648681).

Almost surely, 2^81729814 is an apocalyptic number.

81729814 is the 7382-nd centered triangular number.

81729814 is a deficient number, since it is larger than the sum of its proper divisors (40864910).

81729814 is a wasteful number, since it uses less digits than its factorization.

81729814 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40864909.

The product of its digits is 32256, while the sum is 40.

The square root of 81729814 is about 9040.4543027439. The cubic root of 81729814 is about 433.9704617215.

The spelling of 81729814 in words is "eighty-one million, seven hundred twenty-nine thousand, eight hundred fourteen".