81851540 has 24 divisors (see below), whose sum is σ = 173130720. Its totient is φ = 32503968.

The previous prime is 81851537. The next prime is 81851573. The reversal of 81851540 is 4515818.

It is a junction number, because it is equal to n+sod(n) for n = 81851497 and 81851506.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11942 + ... + 17501.

It is an arithmetic number, because the mean of its divisors is an integer number (7213780).

Almost surely, 2^81851540 is an apocalyptic number.

It is an amenable number.

81851540 is an abundant number, since it is smaller than the sum of its proper divisors (91279180).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81851540 is a wasteful number, since it uses less digits than its factorization.

81851540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29591 (or 29589 counting only the distinct ones).

The product of its (nonzero) digits is 6400, while the sum is 32.

The square root of 81851540 is about 9047.1840923019. The cubic root of 81851540 is about 434.1858024967.

The spelling of 81851540 in words is "eighty-one million, eight hundred fifty-one thousand, five hundred forty".