19775809 has 3 divisors (see below), whose sum is σ = 19780257. Its totient is φ = 19771362.

The previous prime is 19775801. The next prime is 19775831. The reversal of 19775809 is 90857791.

The square root of 19775809 is 4447.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 90857791 = 19 ⋅4781989.

It is not a de Polignac number, because 19775809 - 2³ = 19775801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19775801) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2224 + ... + 6670.

It is an arithmetic number, because the mean of its divisors is an integer number (6593419).

Almost surely, 2^19775809 is an apocalyptic number.

19775809 is the 4447-th square number.

19775809 is the 2224-th centered octagonal number.

It is an amenable number.

19775809 is a deficient number, since it is larger than the sum of its proper divisors (4448).

19775809 is an frugal number, since it uses more digits than its factorization.

19775809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8894 (or 4447 counting only the distinct ones).

The product of its (nonzero) digits is 158760, while the sum is 46.

The cubic root of 19775809 is about 270.4237014648.

The spelling of 19775809 in words is "nineteen million, seven hundred seventy-five thousand, eight hundred nine".