81779407 has 2 divisors, whose sum is σ = 81779408. Its totient is φ = 81779406.

The previous prime is 81779393. The next prime is 81779417. The reversal of 81779407 is 70497718.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81779407 - 2²³ = 73390799 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81779417) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40889703 + 40889704.

It is an arithmetic number, because the mean of its divisors is an integer number (40889704).

Almost surely, 2^81779407 is an apocalyptic number.

81779407 is a deficient number, since it is larger than the sum of its proper divisors (1).

81779407 is an equidigital number, since it uses as much as digits as its factorization.

81779407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 98784, while the sum is 43.

The square root of 81779407 is about 9043.1967246102. The cubic root of 81779407 is about 434.0582205796.

The spelling of 81779407 in words is "eighty-one million, seven hundred seventy-nine thousand, four hundred seven".