81521383 has 4 divisors (see below), whose sum is σ = 81859888. Its totient is φ = 81182880.

The previous prime is 81521371. The next prime is 81521387. The reversal of 81521383 is 38312518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 38312518 = 2 ⋅19156259.

It is a cyclic number.

It is not a de Polignac number, because 81521383 - 2¹³ = 81513191 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81521387) 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, 168891 + ... + 169372.

It is an arithmetic number, because the mean of its divisors is an integer number (20464972).

Almost surely, 2^81521383 is an apocalyptic number.

81521383 is a deficient number, since it is larger than the sum of its proper divisors (338505).

81521383 is a wasteful number, since it uses less digits than its factorization.

81521383 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338504.

The product of its digits is 5760, while the sum is 31.

The square root of 81521383 is about 9028.9192598007. The cubic root of 81521383 is about 433.6012374269.

The spelling of 81521383 in words is "eighty-one million, five hundred twenty-one thousand, three hundred eighty-three".