81661451 has 2 divisors, whose sum is σ = 81661452. Its totient is φ = 81661450.

The previous prime is 81661439. The next prime is 81661457. The reversal of 81661451 is 15416618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81661451 - 2¹⁰ = 81660427 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81661457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40830725 + 40830726.

It is an arithmetic number, because the mean of its divisors is an integer number (40830726).

Almost surely, 2^81661451 is an apocalyptic number.

81661451 is a deficient number, since it is larger than the sum of its proper divisors (1).

81661451 is an equidigital number, since it uses as much as digits as its factorization.

81661451 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5760, while the sum is 32.

The square root of 81661451 is about 9036.6725623982. The cubic root of 81661451 is about 433.8494296000.

The spelling of 81661451 in words is "eighty-one million, six hundred sixty-one thousand, four hundred fifty-one".