13661991 has 24 divisors (see below), whose sum is σ = 23166624. Its totient is φ = 7594560.

The previous prime is 13661971. The next prime is 13662013. The reversal of 13661991 is 19916631.

13661991 is a `hidden beast` number, since 1 + 36 + 619 + 9 + 1 = 666.

It is not a de Polignac number, because 13661991 - 2⁶ = 13661927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13661941) 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 23 ways as a sum of consecutive naturals, for example, 600 + ... + 5261.

It is an arithmetic number, because the mean of its divisors is an integer number (965276).

Almost surely, 2^13661991 is an apocalyptic number.

13661991 is a deficient number, since it is larger than the sum of its proper divisors (9504633).

13661991 is a wasteful number, since it uses less digits than its factorization.

13661991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5911 (or 5908 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 13661991 is about 3696.2130620407. The cubic root of 13661991 is about 239.0587613666.

The spelling of 13661991 in words is "thirteen million, six hundred sixty-one thousand, nine hundred ninety-one".