81211389 has 8 divisors (see below), whose sum is σ = 123750720. Its totient is φ = 46406496.

The previous prime is 81211387. The next prime is 81211393. The reversal of 81211389 is 98311218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81211389 - 2¹ = 81211387 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81211387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1933584 + ... + 1933625.

It is an arithmetic number, because the mean of its divisors is an integer number (15468840).

Almost surely, 2^81211389 is an apocalyptic number.

It is an amenable number.

81211389 is a deficient number, since it is larger than the sum of its proper divisors (42539331).

81211389 is a wasteful number, since it uses less digits than its factorization.

81211389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3867219.

The product of its digits is 3456, while the sum is 33.

The square root of 81211389 is about 9011.7361812250. The cubic root of 81211389 is about 433.0509338858.

The spelling of 81211389 in words is "eighty-one million, two hundred eleven thousand, three hundred eighty-nine".