81521837 has 8 divisors (see below), whose sum is σ = 85976160. Its totient is φ = 77083920.

The previous prime is 81521831. The next prime is 81521873. The reversal of 81521837 is 73812518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81521837 - 2⁶ = 81521773 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81521797 and 81521806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81521831) 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 7 ways as a sum of consecutive naturals, for example, 6887 + ... + 14507.

It is an arithmetic number, because the mean of its divisors is an integer number (10747020).

Almost surely, 2^81521837 is an apocalyptic number.

It is an amenable number.

81521837 is a deficient number, since it is larger than the sum of its proper divisors (4454323).

81521837 is a wasteful number, since it uses less digits than its factorization.

81521837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8203.

The product of its digits is 13440, while the sum is 35.

The square root of 81521837 is about 9028.9444012022. The cubic root of 81521837 is about 433.6020423469.

The spelling of 81521837 in words is "eighty-one million, five hundred twenty-one thousand, eight hundred thirty-seven".