81647978446 has 4 divisors (see below), whose sum is σ = 122471967672. Its totient is φ = 40823989222.

The previous prime is 81647978443. The next prime is 81647978449. The reversal of 81647978446 is 64487974618.

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

It is an interprime number because it is at equal distance from previous prime (81647978443) and next prime (81647978449).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81647978443) 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 as a sum of consecutive naturals, namely, 20411994610 + ... + 20411994613.

It is an arithmetic number, because the mean of its divisors is an integer number (30617991918).

Almost surely, 2^81647978446 is an apocalyptic number.

81647978446 is a deficient number, since it is larger than the sum of its proper divisors (40823989226).

81647978446 is a wasteful number, since it uses less digits than its factorization.

81647978446 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40823989225.

The product of its digits is 65028096, while the sum is 64.

The spelling of 81647978446 in words is "eighty-one billion, six hundred forty-seven million, nine hundred seventy-eight thousand, four hundred forty-six".