81287515 has 4 divisors (see below), whose sum is σ = 97545024. Its totient is φ = 65030008.

The previous prime is 81287467. The next prime is 81287593. The reversal of 81287515 is 51578218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 51578218 = 2 ⋅25789109.

It is a cyclic number.

It is not a de Polignac number, because 81287515 - 2¹³ = 81279323 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8128747 + ... + 8128756.

It is an arithmetic number, because the mean of its divisors is an integer number (24386256).

Almost surely, 2^81287515 is an apocalyptic number.

81287515 is a deficient number, since it is larger than the sum of its proper divisors (16257509).

81287515 is a wasteful number, since it uses less digits than its factorization.

81287515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16257508.

The product of its digits is 22400, while the sum is 37.

The square root of 81287515 is about 9015.9589062950. The cubic root of 81287515 is about 433.1862028444.

The spelling of 81287515 in words is "eighty-one million, two hundred eighty-seven thousand, five hundred fifteen".