81815651 has 2 divisors, whose sum is σ = 81815652. Its totient is φ = 81815650.

The previous prime is 81815633. The next prime is 81815659. The reversal of 81815651 is 15651818.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81815651 - 2²² = 77621347 is a prime.

It is not a weakly prime, because it can be changed into another prime (81815659) 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, 40907825 + 40907826.

It is an arithmetic number, because the mean of its divisors is an integer number (40907826).

Almost surely, 2^81815651 is an apocalyptic number.

81815651 is a deficient number, since it is larger than the sum of its proper divisors (1).

81815651 is an equidigital number, since it uses as much as digits as its factorization.

81815651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9600, while the sum is 35.

The square root of 81815651 is about 9045.2004400124. The cubic root of 81815651 is about 434.1223348565.

The spelling of 81815651 in words is "eighty-one million, eight hundred fifteen thousand, six hundred fifty-one".