81491545 has 4 divisors (see below), whose sum is σ = 97789860. Its totient is φ = 65193232.

The previous prime is 81491519. The next prime is 81491569. The reversal of 81491545 is 54519418.

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 57881664 + 23609881 = 7608^2 + 4859^2 .

It is a cyclic number.

It is not a de Polignac number, because 81491545 - 2¹⁷ = 81360473 is a prime.

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, 8149150 + ... + 8149159.

It is an arithmetic number, because the mean of its divisors is an integer number (24447465).

Almost surely, 2^81491545 is an apocalyptic number.

It is an amenable number.

81491545 is a deficient number, since it is larger than the sum of its proper divisors (16298315).

81491545 is a wasteful number, since it uses less digits than its factorization.

81491545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16298314.

The product of its digits is 28800, while the sum is 37.

The square root of 81491545 is about 9027.2667513484. The cubic root of 81491545 is about 433.5483295392.

The spelling of 81491545 in words is "eighty-one million, four hundred ninety-one thousand, five hundred forty-five".