81851913 has 24 divisors (see below), whose sum is σ = 138902400. Its totient is φ = 45790560.

The previous prime is 81851893. The next prime is 81851941. The reversal of 81851913 is 31915818.

It is not a de Polignac number, because 81851913 - 2¹³ = 81843721 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81851953) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 30513 + ... + 33086.

It is an arithmetic number, because the mean of its divisors is an integer number (5787600).

Almost surely, 2^81851913 is an apocalyptic number.

It is an amenable number.

81851913 is a deficient number, since it is larger than the sum of its proper divisors (57050487).

81851913 is a wasteful number, since it uses less digits than its factorization.

81851913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63629 (or 63626 counting only the distinct ones).

The product of its digits is 8640, while the sum is 36.

The square root of 81851913 is about 9047.2047064273. The cubic root of 81851913 is about 434.1864620284.

The spelling of 81851913 in words is "eighty-one million, eight hundred fifty-one thousand, nine hundred thirteen".