81218845 has 4 divisors (see below), whose sum is σ = 97462620. Its totient is φ = 64975072.

The previous prime is 81218801. The next prime is 81218897. The reversal of 81218845 is 54881218.

It is a happy number.

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 25775929 + 55442916 = 5077^2 + 7446^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81218845 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8121880 + ... + 8121889.

It is an arithmetic number, because the mean of its divisors is an integer number (24365655).

Almost surely, 2^81218845 is an apocalyptic number.

It is an amenable number.

81218845 is a deficient number, since it is larger than the sum of its proper divisors (16243775).

81218845 is a wasteful number, since it uses less digits than its factorization.

81218845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16243774.

The product of its digits is 20480, while the sum is 37.

The square root of 81218845 is about 9012.1498545020. The cubic root of 81218845 is about 433.0641862510.

The spelling of 81218845 in words is "eighty-one million, two hundred eighteen thousand, eight hundred forty-five".