81877394749 has 4 divisors (see below), whose sum is σ = 82168773660. Its totient is φ = 81586015840.

The previous prime is 81877394747. The next prime is 81877394759. The reversal of 81877394749 is 94749377818.

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

It can be written as a sum of positive squares in 2 ways, for example, as 28091436025 + 53785958724 = 167605^2 + 231918^2 .

It is a cyclic number.

It is not a de Polignac number, because 81877394749 - 2¹ = 81877394747 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 (81877394747) 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 3 ways as a sum of consecutive naturals, for example, 145689034 + ... + 145689595.

It is an arithmetic number, because the mean of its divisors is an integer number (20542193415).

Almost surely, 2^81877394749 is an apocalyptic number.

It is an amenable number.

81877394749 is a deficient number, since it is larger than the sum of its proper divisors (291378911).

81877394749 is a wasteful number, since it uses less digits than its factorization.

81877394749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291378910.

The product of its digits is 85349376, while the sum is 67.

The spelling of 81877394749 in words is "eighty-one billion, eight hundred seventy-seven million, three hundred ninety-four thousand, seven hundred forty-nine".