81951107491 has 8 divisors (see below), whose sum is σ = 89505537264. Its totient is φ = 74414065920.

The previous prime is 81951107479. The next prime is 81951107531. The reversal of 81951107491 is 19470115918.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81951107491 - 2¹³ = 81951099299 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81951107471) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4337190 + ... + 4356043.

It is an arithmetic number, because the mean of its divisors is an integer number (11188192158).

Almost surely, 2^81951107491 is an apocalyptic number.

81951107491 is a deficient number, since it is larger than the sum of its proper divisors (7554429773).

81951107491 is a wasteful number, since it uses less digits than its factorization.

81951107491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8694101.

The product of its (nonzero) digits is 90720, while the sum is 46.

The spelling of 81951107491 in words is "eighty-one billion, nine hundred fifty-one million, one hundred seven thousand, four hundred ninety-one".