19685661 has 4 divisors (see below), whose sum is σ = 26247552. Its totient is φ = 13123772.

The previous prime is 19685647. The next prime is 19685671. The reversal of 19685661 is 16658691.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19685661 - 2¹⁴ = 19669277 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19685641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3280941 + ... + 3280946.

It is an arithmetic number, because the mean of its divisors is an integer number (6561888).

Almost surely, 2^19685661 is an apocalyptic number.

It is an amenable number.

19685661 is a deficient number, since it is larger than the sum of its proper divisors (6561891).

19685661 is an equidigital number, since it uses as much as digits as its factorization.

19685661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6561890.

The product of its digits is 77760, while the sum is 42.

The square root of 19685661 is about 4436.8526006619. The cubic root of 19685661 is about 270.0121668043.

The spelling of 19685661 in words is "nineteen million, six hundred eighty-five thousand, six hundred sixty-one".