81219211 has 4 divisors (see below), whose sum is σ = 81375624. Its totient is φ = 81062800.

The previous prime is 81219197. The next prime is 81219253. The reversal of 81219211 is 11291218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11291218 = 2 ⋅5645609.

It is a cyclic number.

It is not a de Polignac number, because 81219211 - 2⁵ = 81219179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (82219211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77425 + ... + 78466.

It is an arithmetic number, because the mean of its divisors is an integer number (20343906).

Almost surely, 2^81219211 is an apocalyptic number.

81219211 is a deficient number, since it is larger than the sum of its proper divisors (156413).

81219211 is a wasteful number, since it uses less digits than its factorization.

81219211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156412.

The product of its digits is 288, while the sum is 25.

The square root of 81219211 is about 9012.1701603998. The cubic root of 81219211 is about 433.0648367620.

The spelling of 81219211 in words is "eighty-one million, two hundred nineteen thousand, two hundred eleven".