19661643 has 8 divisors (see below), whose sum is σ = 29128400. Its totient is φ = 13107744.

The previous prime is 19661641. The next prime is 19661647. The reversal of 19661643 is 34616691.

19661643 is a `hidden beast` number, since 1 + 9 + 6 + 6 + 1 + 643 = 666.

It is not a de Polignac number, because 19661643 - 2¹ = 19661641 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19661598 and 19661607.

It is not an unprimeable number, because it can be changed into a prime (19661641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 364078 + ... + 364131.

It is an arithmetic number, because the mean of its divisors is an integer number (3641050).

Almost surely, 2^19661643 is an apocalyptic number.

19661643 is a deficient number, since it is larger than the sum of its proper divisors (9466757).

19661643 is an equidigital number, since it uses as much as digits as its factorization.

19661643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 728218 (or 728212 counting only the distinct ones).

The product of its digits is 23328, while the sum is 36.

The square root of 19661643 is about 4434.1451261771. The cubic root of 19661643 is about 269.9023103378.

The spelling of 19661643 in words is "nineteen million, six hundred sixty-one thousand, six hundred forty-three".