81540521 has 4 divisors (see below), whose sum is σ = 81651600. Its totient is φ = 81429444.

The previous prime is 81540499. The next prime is 81540523. The reversal of 81540521 is 12504518.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81540521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81540523) 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, 54431 + ... + 55908.

It is an arithmetic number, because the mean of its divisors is an integer number (20412900).

Almost surely, 2^81540521 is an apocalyptic number.

It is an amenable number.

81540521 is a deficient number, since it is larger than the sum of its proper divisors (111079).

81540521 is a wasteful number, since it uses less digits than its factorization.

81540521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111078.

The product of its (nonzero) digits is 1600, while the sum is 26.

The square root of 81540521 is about 9029.9790143721. The cubic root of 81540521 is about 433.6351655853.

The spelling of 81540521 in words is "eighty-one million, five hundred forty thousand, five hundred twenty-one".