81238521 has 32 divisors (see below), whose sum is σ = 136057600. Its totient is φ = 42844032.

The previous prime is 81238501. The next prime is 81238523. The reversal of 81238521 is 12583218.

It is not a de Polignac number, because 81238521 - 2⁵ = 81238489 is a prime.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81238523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10341 + ... + 16413.

It is an arithmetic number, because the mean of its divisors is an integer number (4251800).

Almost surely, 2^81238521 is an apocalyptic number.

It is an amenable number.

81238521 is a deficient number, since it is larger than the sum of its proper divisors (54819079).

81238521 is a wasteful number, since it uses less digits than its factorization.

81238521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6110 (or 6096 counting only the distinct ones).

The product of its digits is 3840, while the sum is 30.

The square root of 81238521 is about 9013.2414258135. The cubic root of 81238521 is about 433.0991546663.

The spelling of 81238521 in words is "eighty-one million, two hundred thirty-eight thousand, five hundred twenty-one".