81954391 has 4 divisors (see below), whose sum is σ = 86267800. Its totient is φ = 77640984.

The previous prime is 81954349. The next prime is 81954413. The reversal of 81954391 is 19345918.

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 81954391 - 2¹⁷ = 81823319 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 (81954311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2156676 + ... + 2156713.

It is an arithmetic number, because the mean of its divisors is an integer number (21566950).

Almost surely, 2^81954391 is an apocalyptic number.

81954391 is a deficient number, since it is larger than the sum of its proper divisors (4313409).

81954391 is a wasteful number, since it uses less digits than its factorization.

81954391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4313408.

The product of its digits is 38880, while the sum is 40.

The square root of 81954391 is about 9052.8664521244. The cubic root of 81954391 is about 434.3675858921.

The spelling of 81954391 in words is "eighty-one million, nine hundred fifty-four thousand, three hundred ninety-one".