19666643 has 2 divisors, whose sum is σ = 19666644. Its totient is φ = 19666642.

The previous prime is 19666639. The next prime is 19666651. The reversal of 19666643 is 34666691.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19666643 - 2² = 19666639 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19666643.

It is not a weakly prime, because it can be changed into another prime (19666613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9833321 + 9833322.

It is an arithmetic number, because the mean of its divisors is an integer number (9833322).

Almost surely, 2^19666643 is an apocalyptic number.

19666643 is a deficient number, since it is larger than the sum of its proper divisors (1).

19666643 is an equidigital number, since it uses as much as digits as its factorization.

19666643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 139968, while the sum is 41.

The square root of 19666643 is about 4434.7088968725. The cubic root of 19666643 is about 269.9251873201.

The spelling of 19666643 in words is "nineteen million, six hundred sixty-six thousand, six hundred forty-three".