19788661 has 4 divisors (see below), whose sum is σ = 19805152. Its totient is φ = 19772172.

The previous prime is 19788653. The next prime is 19788683. The reversal of 19788661 is 16688791.

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 19788661 - 2³ = 19788653 is a prime.

It is a super-2 number, since 2×19788661² = 783182208345842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19788061) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6291 + ... + 8896.

It is an arithmetic number, because the mean of its divisors is an integer number (4951288).

Almost surely, 2^19788661 is an apocalyptic number.

It is an amenable number.

19788661 is a deficient number, since it is larger than the sum of its proper divisors (16491).

19788661 is a wasteful number, since it uses less digits than its factorization.

19788661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16490.

The product of its digits is 145152, while the sum is 46.

The square root of 19788661 is about 4448.4447844162. Note that the first 3 decimals coincide. The cubic root of 19788661 is about 270.4822702073.

It can be divided in two parts, 19788 and 661, that added together give a square (20449 = 143²).

The spelling of 19788661 in words is "nineteen million, seven hundred eighty-eight thousand, six hundred sixty-one".