81638777 has 8 divisors (see below), whose sum is σ = 94299552. Its totient is φ = 69851200.

The previous prime is 81638759. The next prime is 81638803. The reversal of 81638777 is 77783618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81638777 - 2¹⁰ = 81637753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81638737) 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 in 7 ways as a sum of consecutive naturals, for example, 218099 + ... + 218472.

It is an arithmetic number, because the mean of its divisors is an integer number (11787444).

Almost surely, 2^81638777 is an apocalyptic number.

It is an amenable number.

81638777 is a deficient number, since it is larger than the sum of its proper divisors (12660775).

81638777 is a wasteful number, since it uses less digits than its factorization.

81638777 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 436599.

The product of its digits is 395136, while the sum is 47.

The square root of 81638777 is about 9035.4179206056. The cubic root of 81638777 is about 433.8092718820.

It can be divided in two parts, 816 and 38777, that added together give a palindrome (39593).

The spelling of 81638777 in words is "eighty-one million, six hundred thirty-eight thousand, seven hundred seventy-seven".