20509919 has 2 divisors, whose sum is σ = 20509920. Its totient is φ = 20509918.

The previous prime is 20509903. The next prime is 20509921. The reversal of 20509919 is 91990502.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20509919 - 2⁴ = 20509903 is a prime.

It is a super-2 number, since 2×20509919² = 841313554773122, which contains 22 as substring.

Together with 20509921, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20509319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10254959 + 10254960.

It is an arithmetic number, because the mean of its divisors is an integer number (10254960).

Almost surely, 2^20509919 is an apocalyptic number.

20509919 is a deficient number, since it is larger than the sum of its proper divisors (1).

20509919 is an equidigital number, since it uses as much as digits as its factorization.

20509919 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7290, while the sum is 35.

The square root of 20509919 is about 4528.7878069082. The cubic root of 20509919 is about 273.7293178150.

The spelling of 20509919 in words is "twenty million, five hundred nine thousand, nine hundred nineteen".