19897666 has 4 divisors (see below), whose sum is σ = 29846502. Its totient is φ = 9948832.

The previous prime is 19897663. The next prime is 19897699. The reversal of 19897666 is 66679891.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 13111641 + 6786025 = 3621^2 + 2605^2 .

It is a super-2 number, since 2×19897666² = 791834224495112, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19897663) 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 as a sum of consecutive naturals, namely, 4974415 + ... + 4974418.

Almost surely, 2^19897666 is an apocalyptic number.

19897666 is a deficient number, since it is larger than the sum of its proper divisors (9948836).

19897666 is an equidigital number, since it uses as much as digits as its factorization.

19897666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9948835.

The product of its digits is 979776, while the sum is 52.

The square root of 19897666 is about 4460.6799930056. The cubic root of 19897666 is about 270.9780077740.

The spelling of 19897666 in words is "nineteen million, eight hundred ninety-seven thousand, six hundred sixty-six".