1318721686 has 4 divisors (see below), whose sum is σ = 1978082532. Its totient is φ = 659360842.

The previous prime is 1318721683. The next prime is 1318721689. The reversal of 1318721686 is 6861278131.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6861278131 = 197 ⋅34828823.

It is an interprime number because it is at equal distance from previous prime (1318721683) and next prime (1318721689).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1318721681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 329680420 + ... + 329680423.

It is an arithmetic number, because the mean of its divisors is an integer number (494520633).

Almost surely, 2^1318721686 is an apocalyptic number.

1318721686 is a deficient number, since it is larger than the sum of its proper divisors (659360846).

1318721686 is an equidigital number, since it uses as much as digits as its factorization.

1318721686 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 659360845.

The product of its digits is 96768, while the sum is 43.

The square root of 1318721686 is about 36314.2077705132. The cubic root of 1318721686 is about 1096.6070898038.

The spelling of 1318721686 in words is "one billion, three hundred eighteen million, seven hundred twenty-one thousand, six hundred eighty-six".