81779567 has 4 divisors (see below), whose sum is σ = 81814200. Its totient is φ = 81744936.

The previous prime is 81779561. The next prime is 81779603. The reversal of 81779567 is 76597718.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81779567 - 2²⁴ = 65002351 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 (81779561) 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, 13493 + ... + 18590.

It is an arithmetic number, because the mean of its divisors is an integer number (20453550).

Almost surely, 2^81779567 is an apocalyptic number.

81779567 is a deficient number, since it is larger than the sum of its proper divisors (34633).

81779567 is a wasteful number, since it uses less digits than its factorization.

81779567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34632.

The product of its digits is 740880, while the sum is 50.

The square root of 81779567 is about 9043.2055710351. The cubic root of 81779567 is about 434.0585036553.

The spelling of 81779567 in words is "eighty-one million, seven hundred seventy-nine thousand, five hundred sixty-seven".