81006491 has 2 divisors, whose sum is σ = 81006492. Its totient is φ = 81006490.

The previous prime is 81006463. The next prime is 81006577. The reversal of 81006491 is 19460018.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81006491 - 2¹⁰ = 81005467 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81006451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40503245 + 40503246.

It is an arithmetic number, because the mean of its divisors is an integer number (40503246).

Almost surely, 2^81006491 is an apocalyptic number.

81006491 is a deficient number, since it is larger than the sum of its proper divisors (1).

81006491 is an equidigital number, since it uses as much as digits as its factorization.

81006491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 81006491 is about 9000.3606038869. The cubic root of 81006491 is about 432.6864283662.

The spelling of 81006491 in words is "eighty-one million, six thousand, four hundred ninety-one".