81671739 has 4 divisors (see below), whose sum is σ = 108895656. Its totient is φ = 54447824.

The previous prime is 81671729. The next prime is 81671771. The reversal of 81671739 is 93717618.

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 81671739 - 2¹⁵ = 81638971 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81671739.

It is not an unprimeable number, because it can be changed into a prime (81671729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13611954 + ... + 13611959.

It is an arithmetic number, because the mean of its divisors is an integer number (27223914).

Almost surely, 2^81671739 is an apocalyptic number.

81671739 is a deficient number, since it is larger than the sum of its proper divisors (27223917).

81671739 is a wasteful number, since it uses less digits than its factorization.

81671739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27223916.

The product of its digits is 63504, while the sum is 42.

The square root of 81671739 is about 9037.2417805434. The cubic root of 81671739 is about 433.8676481329.

The spelling of 81671739 in words is "eighty-one million, six hundred seventy-one thousand, seven hundred thirty-nine".