81491085 has 24 divisors (see below), whose sum is σ = 152117784. Its totient is φ = 40118400.

The previous prime is 81491083. The next prime is 81491099. The reversal of 81491085 is 58019418.

It can be written as a sum of positive squares in 4 ways, for example, as 11634921 + 69856164 = 3411^2 + 8358^2 .

It is not a de Polignac number, because 81491085 - 2¹ = 81491083 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81491083) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 69066 + ... + 70235.

It is an arithmetic number, because the mean of its divisors is an integer number (6338241).

Almost surely, 2^81491085 is an apocalyptic number.

It is an amenable number.

81491085 is a deficient number, since it is larger than the sum of its proper divisors (70626699).

81491085 is a wasteful number, since it uses less digits than its factorization.

81491085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139325 (or 139322 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 81491085 is about 9027.2412729471. The cubic root of 81491085 is about 433.5475137793.

The spelling of 81491085 in words is "eighty-one million, four hundred ninety-one thousand, eighty-five".