81789077 has 4 divisors (see below), whose sum is σ = 84609420. Its totient is φ = 78968736.

The previous prime is 81789073. The next prime is 81789079. The reversal of 81789077 is 77098718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 77098718 = 2 ⋅38549359.

It can be written as a sum of positive squares in 2 ways, for example, as 12716356 + 69072721 = 3566^2 + 8311^2 .

It is a cyclic number.

It is not a de Polignac number, because 81789077 - 2² = 81789073 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81789073) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1410128 + ... + 1410185.

It is an arithmetic number, because the mean of its divisors is an integer number (21152355).

Almost surely, 2^81789077 is an apocalyptic number.

It is an amenable number.

81789077 is a deficient number, since it is larger than the sum of its proper divisors (2820343).

81789077 is a wasteful number, since it uses less digits than its factorization.

81789077 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2820342.

The product of its (nonzero) digits is 197568, while the sum is 47.

The square root of 81789077 is about 9043.7313648737. The cubic root of 81789077 is about 434.0753282995.

The spelling of 81789077 in words is "eighty-one million, seven hundred eighty-nine thousand, seventy-seven".