81681335 has 4 divisors (see below), whose sum is σ = 98017608. Its totient is φ = 65345064.

The previous prime is 81681329. The next prime is 81681343. The reversal of 81681335 is 53318618.

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

It is a cyclic number.

It is not a de Polignac number, because 81681335 - 2⁴ = 81681319 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81681295 and 81681304.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8168129 + ... + 8168138.

It is an arithmetic number, because the mean of its divisors is an integer number (24504402).

Almost surely, 2^81681335 is an apocalyptic number.

81681335 is a deficient number, since it is larger than the sum of its proper divisors (16336273).

81681335 is a wasteful number, since it uses less digits than its factorization.

81681335 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16336272.

The product of its digits is 17280, while the sum is 35.

The square root of 81681335 is about 9037.7726791505. The cubic root of 81681335 is about 433.8846398567.

The spelling of 81681335 in words is "eighty-one million, six hundred eighty-one thousand, three hundred thirty-five".