81521797 has 4 divisors (see below), whose sum is σ = 93167776. Its totient is φ = 69875820.

The previous prime is 81521773. The next prime is 81521827. The reversal of 81521797 is 79712518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81521797 - 2¹⁵ = 81489029 is a prime.

It is a super-3 number, since 3×81521797³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81521707) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5822979 + ... + 5822992.

It is an arithmetic number, because the mean of its divisors is an integer number (23291944).

Almost surely, 2^81521797 is an apocalyptic number.

It is an amenable number.

81521797 is a deficient number, since it is larger than the sum of its proper divisors (11645979).

81521797 is a wasteful number, since it uses less digits than its factorization.

81521797 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11645978.

The product of its digits is 35280, while the sum is 40.

The square root of 81521797 is about 9028.9421861035. The cubic root of 81521797 is about 433.6019714290.

The spelling of 81521797 in words is "eighty-one million, five hundred twenty-one thousand, seven hundred ninety-seven".