81678981 has 4 divisors (see below), whose sum is σ = 108905312. Its totient is φ = 54452652.

The previous prime is 81678977. The next prime is 81678983. The reversal of 81678981 is 18987618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81678981 - 2² = 81678977 is a prime.

It is a super-2 number, since 2×81678981² = 13342911874396722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81678981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81678983) 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, 13613161 + ... + 13613166.

It is an arithmetic number, because the mean of its divisors is an integer number (27226328).

Almost surely, 2^81678981 is an apocalyptic number.

It is an amenable number.

81678981 is a deficient number, since it is larger than the sum of its proper divisors (27226331).

81678981 is a wasteful number, since it uses less digits than its factorization.

81678981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27226330.

The product of its digits is 193536, while the sum is 48.

The square root of 81678981 is about 9037.6424470102. The cubic root of 81678981 is about 433.8804717309.

It can be divided in two parts, 816 and 78981, that added together give a palindrome (79797).

The spelling of 81678981 in words is "eighty-one million, six hundred seventy-eight thousand, nine hundred eighty-one".