81315263 has 4 divisors (see below), whose sum is σ = 83938368. Its totient is φ = 78692160.

The previous prime is 81315251. The next prime is 81315293. The reversal of 81315263 is 36251318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 36251318 = 2 ⋅18125659.

It is a cyclic number.

It is not a de Polignac number, because 81315263 - 2⁸ = 81315007 is a prime.

It is a super-2 number, since 2×81315263² = 13224343993518338, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81315293) 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, 1311506 + ... + 1311567.

It is an arithmetic number, because the mean of its divisors is an integer number (20984592).

Almost surely, 2^81315263 is an apocalyptic number.

81315263 is a deficient number, since it is larger than the sum of its proper divisors (2623105).

81315263 is a wasteful number, since it uses less digits than its factorization.

81315263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2623104.

The product of its digits is 4320, while the sum is 29.

The square root of 81315263 is about 9017.4976018849. The cubic root of 81315263 is about 433.2354875072.

The spelling of 81315263 in words is "eighty-one million, three hundred fifteen thousand, two hundred sixty-three".