81900000891 has 12 divisors (see below), whose sum is σ = 120065673832. Its totient is φ = 53785074816.

The previous prime is 81900000839. The next prime is 81900000947. The reversal of 81900000891 is 19800000918.

It is not a de Polignac number, because 81900000891 - 2⁶ = 81900000827 is a prime.

It is a super-2 number, since 2×81900000891² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

81900000891 is a modest number, since divided by 891 gives 819 as remainder.

It is not an unprimeable number, because it can be changed into a prime (81900000691) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67909846 + ... + 67911051.

Almost surely, 2^81900000891 is an apocalyptic number.

81900000891 is a deficient number, since it is larger than the sum of its proper divisors (38165672941).

81900000891 is a wasteful number, since it uses less digits than its factorization.

81900000891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135820970 (or 135820967 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 36.

The spelling of 81900000891 in words is "eighty-one billion, nine hundred million, eight hundred ninety-one", and thus it is an aban number.