81777645 has 12 divisors (see below), whose sum is σ = 141747996. Its totient is φ = 43614720.

The previous prime is 81777643. The next prime is 81777649. The reversal of 81777645 is 54677718.

It can be written as a sum of positive squares in 2 ways, for example, as 30669444 + 51108201 = 5538^2 + 7149^2 .

It is not a de Polignac number, because 81777645 - 2¹ = 81777643 is a prime.

It is a super-3 number, since 3×81777645³ (a number of 25 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 1817281 = 81777645 / (8 + 1 + 7 + 7 + 7 + 6 + 4 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 81777645.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81777643) 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 in 11 ways as a sum of consecutive naturals, for example, 908596 + ... + 908685.

It is an arithmetic number, because the mean of its divisors is an integer number (11812333).

Almost surely, 2^81777645 is an apocalyptic number.

It is an amenable number.

81777645 is a deficient number, since it is larger than the sum of its proper divisors (59970351).

81777645 is a wasteful number, since it uses less digits than its factorization.

81777645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1817292 (or 1817289 counting only the distinct ones).

The product of its digits is 329280, while the sum is 45.

The square root of 81777645 is about 9043.0993027833. The cubic root of 81777645 is about 434.0551031849.

The spelling of 81777645 in words is "eighty-one million, seven hundred seventy-seven thousand, six hundred forty-five".