15990665 has 4 divisors (see below), whose sum is σ = 19188804. Its totient is φ = 12792528.

The previous prime is 15990649. The next prime is 15990679. The reversal of 15990665 is 56609951.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56609951 = 7499 ⋅7549.

It can be written as a sum of positive squares in 2 ways, for example, as 11751184 + 4239481 = 3428^2 + 2059^2 .

It is a cyclic number.

It is not a de Polignac number, because 15990665 - 2⁴ = 15990649 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1599062 + ... + 1599071.

It is an arithmetic number, because the mean of its divisors is an integer number (4797201).

Almost surely, 2^15990665 is an apocalyptic number.

It is an amenable number.

15990665 is a deficient number, since it is larger than the sum of its proper divisors (3198139).

15990665 is an equidigital number, since it uses as much as digits as its factorization.

15990665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3198138.

The product of its (nonzero) digits is 72900, while the sum is 41.

The square root of 15990665 is about 3998.8329547507. The cubic root of 15990665 is about 251.9351947661.

The spelling of 15990665 in words is "fifteen million, nine hundred ninety thousand, six hundred sixty-five".