81978772 has 12 divisors (see below), whose sum is σ = 143691156. Its totient is φ = 40924160.

The previous prime is 81978761. The next prime is 81978773. The reversal of 81978772 is 27787918.

It can be written as a sum of positive squares in 2 ways, for example, as 76807696 + 5171076 = 8764^2 + 2274^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81978773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13423 + ... + 18550.

It is an arithmetic number, because the mean of its divisors is an integer number (11974263).

Almost surely, 2^81978772 is an apocalyptic number.

It is an amenable number.

81978772 is a deficient number, since it is larger than the sum of its proper divisors (61712384).

81978772 is a wasteful number, since it uses less digits than its factorization.

81978772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32618 (or 32616 counting only the distinct ones).

The product of its digits is 395136, while the sum is 49.

The square root of 81978772 is about 9054.2129420508. The cubic root of 81978772 is about 434.4106556450.

The spelling of 81978772 in words is "eighty-one million, nine hundred seventy-eight thousand, seven hundred seventy-two".