81749523491 has 4 divisors (see below), whose sum is σ = 81752718000. Its totient is φ = 81746328984.

The previous prime is 81749523439. The next prime is 81749523509. The reversal of 81749523491 is 19432594718.

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 81749523491 - 2³⁴ = 64569654307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81749523421) 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, 1558556 + ... + 1610153.

It is an arithmetic number, because the mean of its divisors is an integer number (20438179500).

Almost surely, 2^81749523491 is an apocalyptic number.

81749523491 is a deficient number, since it is larger than the sum of its proper divisors (3194509).

81749523491 is a wasteful number, since it uses less digits than its factorization.

81749523491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3194508.

The product of its digits is 2177280, while the sum is 53.

The spelling of 81749523491 in words is "eighty-one billion, seven hundred forty-nine million, five hundred twenty-three thousand, four hundred ninety-one".