81938515 has 4 divisors (see below), whose sum is σ = 98326224. Its totient is φ = 65550808.

The previous prime is 81938501. The next prime is 81938533. The reversal of 81938515 is 51583918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81938515 - 2¹¹ = 81936467 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8193847 + ... + 8193856.

It is an arithmetic number, because the mean of its divisors is an integer number (24581556).

Almost surely, 2^81938515 is an apocalyptic number.

81938515 is a deficient number, since it is larger than the sum of its proper divisors (16387709).

81938515 is a wasteful number, since it uses less digits than its factorization.

81938515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16387708.

The product of its digits is 43200, while the sum is 40.

The square root of 81938515 is about 9051.9895603121. The cubic root of 81938515 is about 434.3395358794.

The spelling of 81938515 in words is "eighty-one million, nine hundred thirty-eight thousand, five hundred fifteen".