12991665 has 16 divisors (see below), whose sum is σ = 21691008. Its totient is φ = 6627456.

The previous prime is 12991661. The next prime is 12991673. The reversal of 12991665 is 56619921.

12991665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 12991665 - 2² = 12991661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12991661) 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, 18484 + ... + 19173.

It is an arithmetic number, because the mean of its divisors is an integer number (1355688).

Almost surely, 2^12991665 is an apocalyptic number.

12991665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

12991665 is a deficient number, since it is larger than the sum of its proper divisors (8699343).

12991665 is a wasteful number, since it uses less digits than its factorization.

12991665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37688.

The product of its digits is 29160, while the sum is 39.

The square root of 12991665 is about 3604.3952336002. The cubic root of 12991665 is about 235.0832057858.

The spelling of 12991665 in words is "twelve million, nine hundred ninety-one thousand, six hundred sixty-five".