81904698851 has 4 divisors (see below), whose sum is σ = 82194115032. Its totient is φ = 81615282672.

The previous prime is 81904698751. The next prime is 81904698857. The reversal of 81904698851 is 15889640918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 15889640918 = 2 ⋅7944820459.

It is a cyclic number.

It is not a de Polignac number, because 81904698851 - 2¹⁸ = 81904436707 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81904698857) 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, 144707666 + ... + 144708231.

It is an arithmetic number, because the mean of its divisors is an integer number (20548528758).

Almost surely, 2^81904698851 is an apocalyptic number.

81904698851 is a deficient number, since it is larger than the sum of its proper divisors (289416181).

81904698851 is a wasteful number, since it uses less digits than its factorization.

81904698851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289416180.

The product of its (nonzero) digits is 4976640, while the sum is 59.

The spelling of 81904698851 in words is "eighty-one billion, nine hundred four million, six hundred ninety-eight thousand, eight hundred fifty-one".