81788929 has 2 divisors, whose sum is σ = 81788930. Its totient is φ = 81788928.

The previous prime is 81788923. The next prime is 81788963. The reversal of 81788929 is 92988718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 60840000 + 20948929 = 7800^2 + 4577^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81788929 is a prime.

It is not a weakly prime, because it can be changed into another prime (81788923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40894464 + 40894465.

It is an arithmetic number, because the mean of its divisors is an integer number (40894465).

It is a Proth number, since it is equal to 39 ⋅ 2²¹ + 1 and 39 < 2²¹.

Almost surely, 2^81788929 is an apocalyptic number.

It is an amenable number.

81788929 is a deficient number, since it is larger than the sum of its proper divisors (1).

81788929 is an equidigital number, since it uses as much as digits as its factorization.

81788929 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 580608, while the sum is 52.

The square root of 81788929 is about 9043.7231824067. The cubic root of 81788929 is about 434.0750664749.

The spelling of 81788929 in words is "eighty-one million, seven hundred eighty-eight thousand, nine hundred twenty-nine".