81673651 has 2 divisors, whose sum is σ = 81673652. Its totient is φ = 81673650.

The previous prime is 81673649. The next prime is 81673673. The reversal of 81673651 is 15637618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81673651 - 2¹ = 81673649 is a prime.

Together with 81673649, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 81673651.

It is not a weakly prime, because it can be changed into another prime (81643651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40836825 + 40836826.

It is an arithmetic number, because the mean of its divisors is an integer number (40836826).

Almost surely, 2^81673651 is an apocalyptic number.

81673651 is a deficient number, since it is larger than the sum of its proper divisors (1).

81673651 is an equidigital number, since it uses as much as digits as its factorization.

81673651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 30240, while the sum is 37.

The square root of 81673651 is about 9037.3475644129. The cubic root of 81673651 is about 433.8710338347.

The spelling of 81673651 in words is "eighty-one million, six hundred seventy-three thousand, six hundred fifty-one".