81687313 has 8 divisors (see below), whose sum is σ = 82737000. Its totient is φ = 80644608.

The previous prime is 81687301. The next prime is 81687323. The reversal of 81687313 is 31378618.

It can be written as a sum of positive squares in 4 ways, for example, as 25482304 + 56205009 = 5048^2 + 7497^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81687313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81687323) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24193 + ... + 27361.

It is an arithmetic number, because the mean of its divisors is an integer number (10342125).

Almost surely, 2^81687313 is an apocalyptic number.

It is an amenable number.

81687313 is a deficient number, since it is larger than the sum of its proper divisors (1049687).

81687313 is a wasteful number, since it uses less digits than its factorization.

81687313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3491.

The product of its digits is 24192, while the sum is 37.

The square root of 81687313 is about 9038.1033961778. The cubic root of 81687313 is about 433.8952244826.

The spelling of 81687313 in words is "eighty-one million, six hundred eighty-seven thousand, three hundred thirteen".