13661865 has 80 divisors (see below), whose sum is σ = 28807680. Its totient is φ = 6065280.

The previous prime is 13661861. The next prime is 13661881. The reversal of 13661865 is 56816631.

It is a happy number.

13661865 is a `hidden beast` number, since 1 + 36 + 618 + 6 + 5 = 666.

13661865 is digitally balanced in base 2 and base 8, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 13661865 - 2² = 13661861 is a prime.

13661865 is strictly pandigital in base 8.

It is not an unprimeable number, because it can be changed into a prime (13661861) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 172896 + ... + 172974.

It is an arithmetic number, because the mean of its divisors is an integer number (360096).

Almost surely, 2^13661865 is an apocalyptic number.

13661865 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

13661865 is an abundant number, since it is smaller than the sum of its proper divisors (15145815).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

13661865 is an equidigital number, since it uses as much as digits as its factorization.

13661865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164 (or 155 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 13661865 is about 3696.1960175294. The cubic root of 13661865 is about 239.0580264445.

It can be divided in two parts, 136 and 61865, that added together give a square (62001 = 249²).

The spelling of 13661865 in words is "thirteen million, six hundred sixty-one thousand, eight hundred sixty-five".