81313509 has 4 divisors (see below), whose sum is σ = 108418016. Its totient is φ = 54209004.

The previous prime is 81313493. The next prime is 81313511. The reversal of 81313509 is 90531318.

It is a happy number.

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 not a de Polignac number, because 81313509 - 2⁴ = 81313493 is a prime.

It is a super-2 number, since 2×81313509² = 13223773491786162, 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 (81313109) 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, 13552249 + ... + 13552254.

It is an arithmetic number, because the mean of its divisors is an integer number (27104504).

Almost surely, 2^81313509 is an apocalyptic number.

It is an amenable number.

81313509 is a deficient number, since it is larger than the sum of its proper divisors (27104507).

81313509 is a wasteful number, since it uses less digits than its factorization.

81313509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27104506.

The product of its (nonzero) digits is 3240, while the sum is 30.

The square root of 81313509 is about 9017.4003459977. The cubic root of 81313509 is about 433.2323724688.

The spelling of 81313509 in words is "eighty-one million, three hundred thirteen thousand, five hundred nine".