81148391 has 4 divisors (see below), whose sum is σ = 81229512. Its totient is φ = 81067272.

The previous prime is 81148369. The next prime is 81148399. The reversal of 81148391 is 19384118.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81148391 is a prime.

It is a super-2 number, since 2×81148391² = 13170122723777762, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81148399) 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, 39041 + ... + 41066.

It is an arithmetic number, because the mean of its divisors is an integer number (20307378).

Almost surely, 2^81148391 is an apocalyptic number.

81148391 is a deficient number, since it is larger than the sum of its proper divisors (81121).

81148391 is a wasteful number, since it uses less digits than its factorization.

81148391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81120.

The product of its digits is 6912, while the sum is 35.

The square root of 81148391 is about 9008.2401721979. The cubic root of 81148391 is about 432.9389282487.

The spelling of 81148391 in words is "eighty-one million, one hundred forty-eight thousand, three hundred ninety-one".