81491705 has 4 divisors (see below), whose sum is σ = 97790052. Its totient is φ = 65193360.

The previous prime is 81491701. The next prime is 81491731. The reversal of 81491705 is 50719418.

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

It can be written as a sum of positive squares in 2 ways, for example, as 50310649 + 31181056 = 7093^2 + 5584^2 .

It is not a de Polignac number, because 81491705 - 2² = 81491701 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81491701) 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, 8149166 + ... + 8149175.

It is an arithmetic number, because the mean of its divisors is an integer number (24447513).

Almost surely, 2^81491705 is an apocalyptic number.

It is an amenable number.

81491705 is a deficient number, since it is larger than the sum of its proper divisors (16298347).

81491705 is a wasteful number, since it uses less digits than its factorization.

81491705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16298346.

The product of its (nonzero) digits is 10080, while the sum is 35.

The square root of 81491705 is about 9027.2756133841. The cubic root of 81491705 is about 433.5486132811.

The spelling of 81491705 in words is "eighty-one million, four hundred ninety-one thousand, seven hundred five".