1306685721 has 16 divisors (see below), whose sum is σ = 1906391808. Its totient is φ = 789531600.

The previous prime is 1306685717. The next prime is 1306685749. The reversal of 1306685721 is 1275866031.

It is not a de Polignac number, because 1306685721 - 2² = 1306685717 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1306685721.

It is not an unprimeable number, because it can be changed into a prime (1306685701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48891 + ... + 70736.

It is an arithmetic number, because the mean of its divisors is an integer number (119149488).

Almost surely, 2^1306685721 is an apocalyptic number.

1306685721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1306685721 is a deficient number, since it is larger than the sum of its proper divisors (599706087).

1306685721 is a wasteful number, since it uses less digits than its factorization.

1306685721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119972.

The product of its (nonzero) digits is 60480, while the sum is 39.

The square root of 1306685721 is about 36148.1081247691. The cubic root of 1306685721 is about 1093.2606459357.

The spelling of 1306685721 in words is "one billion, three hundred six million, six hundred eighty-five thousand, seven hundred twenty-one".