81511219 has 2 divisors, whose sum is σ = 81511220. Its totient is φ = 81511218.

The previous prime is 81511217. The next prime is 81511231. The reversal of 81511219 is 91211518.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81511219 - 2¹ = 81511217 is a prime.

It is a super-2 number, since 2×81511219² = 13288157645731922, which contains 22 as substring.

Together with 81511217, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81511211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40755609 + 40755610.

It is an arithmetic number, because the mean of its divisors is an integer number (40755610).

Almost surely, 2^81511219 is an apocalyptic number.

81511219 is a deficient number, since it is larger than the sum of its proper divisors (1).

81511219 is an equidigital number, since it uses as much as digits as its factorization.

81511219 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 28.

The square root of 81511219 is about 9028.3563841931. The cubic root of 81511219 is about 433.5832163630.

The spelling of 81511219 in words is "eighty-one million, five hundred eleven thousand, two hundred nineteen".