81808651 has 2 divisors, whose sum is σ = 81808652. Its totient is φ = 81808650.

The previous prime is 81808637. The next prime is 81808693. The reversal of 81808651 is 15680818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81808651 - 2⁵ = 81808619 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81808651.

It is not a weakly prime, because it can be changed into another prime (81808351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40904325 + 40904326.

It is an arithmetic number, because the mean of its divisors is an integer number (40904326).

Almost surely, 2^81808651 is an apocalyptic number.

81808651 is a deficient number, since it is larger than the sum of its proper divisors (1).

81808651 is an equidigital number, since it uses as much as digits as its factorization.

81808651 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15360, while the sum is 37.

The square root of 81808651 is about 9044.8134861920. The cubic root of 81808651 is about 434.1099535945.

The spelling of 81808651 in words is "eighty-one million, eight hundred eight thousand, six hundred fifty-one".