15680721 has 16 divisors (see below), whose sum is σ = 24288128. Its totient is φ = 8812800.

The previous prime is 15680713. The next prime is 15680741. The reversal of 15680721 is 12708651.

It is not a de Polignac number, because 15680721 - 2³ = 15680713 is a prime.

It is a super-2 number, since 2×15680721² = 491770022159682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15680701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4840 + ... + 7401.

It is an arithmetic number, because the mean of its divisors is an integer number (1518008).

Almost surely, 2^15680721 is an apocalyptic number.

It is an amenable number.

15680721 is a deficient number, since it is larger than the sum of its proper divisors (8607407).

15680721 is a wasteful number, since it uses less digits than its factorization.

15680721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12312.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 15680721 is about 3959.8890135962. The cubic root of 15680721 is about 250.2968261042.

The spelling of 15680721 in words is "fifteen million, six hundred eighty thousand, seven hundred twenty-one".