11681721 has 12 divisors (see below), whose sum is σ = 16979248. Its totient is φ = 7739064.

The previous prime is 11681717. The next prime is 11681729. The reversal of 11681721 is 12718611.

It is not a de Polignac number, because 11681721 - 2² = 11681717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11681729) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2515 + ... + 5448.

Almost surely, 2^11681721 is an apocalyptic number.

It is an amenable number.

11681721 is a deficient number, since it is larger than the sum of its proper divisors (5297527).

11681721 is a wasteful number, since it uses less digits than its factorization.

11681721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8132 (or 8129 counting only the distinct ones).

The product of its digits is 672, while the sum is 27.

The square root of 11681721 is about 3417.8532736207. The cubic root of 11681721 is about 226.9005820025.

The spelling of 11681721 in words is "eleven million, six hundred eighty-one thousand, seven hundred twenty-one".