81263191 has 4 divisors (see below), whose sum is σ = 84065400. Its totient is φ = 78460984.

The previous prime is 81263173. The next prime is 81263197. The reversal of 81263191 is 19136218.

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 81263191 - 2¹¹ = 81261143 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81263197) 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, 1401061 + ... + 1401118.

It is an arithmetic number, because the mean of its divisors is an integer number (21016350).

Almost surely, 2^81263191 is an apocalyptic number.

81263191 is a deficient number, since it is larger than the sum of its proper divisors (2802209).

81263191 is a wasteful number, since it uses less digits than its factorization.

81263191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2802208.

The product of its digits is 2592, while the sum is 31.

The square root of 81263191 is about 9014.6098639930. The cubic root of 81263191 is about 433.1429904996.

The spelling of 81263191 in words is "eighty-one million, two hundred sixty-three thousand, one hundred ninety-one".