81436191 has 4 divisors (see below), whose sum is σ = 108581592. Its totient is φ = 54290792.

The previous prime is 81436181. The next prime is 81436193. The reversal of 81436191 is 19163418.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81436191 - 2¹⁵ = 81403423 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81436193) 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, 13572696 + ... + 13572701.

It is an arithmetic number, because the mean of its divisors is an integer number (27145398).

Almost surely, 2^81436191 is an apocalyptic number.

81436191 is a deficient number, since it is larger than the sum of its proper divisors (27145401).

81436191 is a wasteful number, since it uses less digits than its factorization.

81436191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27145400.

The product of its digits is 5184, while the sum is 33.

The square root of 81436191 is about 9024.2002969792. The cubic root of 81436191 is about 433.4501431975.

The spelling of 81436191 in words is "eighty-one million, four hundred thirty-six thousand, one hundred ninety-one".