20644819 has 4 divisors (see below), whose sum is σ = 22232896. Its totient is φ = 19056744.

The previous prime is 20644807. The next prime is 20644831. The reversal of 20644819 is 91844602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 91844602 = 2 ⋅45922301.

It is an interprime number because it is at equal distance from previous prime (20644807) and next prime (20644831).

It is a cyclic number.

It is not a de Polignac number, because 20644819 - 2¹⁹ = 20120531 is a prime.

It is a super-2 number, since 2×20644819² = 852417103085522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20644889) 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 in 3 ways as a sum of consecutive naturals, for example, 794019 + ... + 794044.

It is an arithmetic number, because the mean of its divisors is an integer number (5558224).

Almost surely, 2^20644819 is an apocalyptic number.

20644819 is a deficient number, since it is larger than the sum of its proper divisors (1588077).

20644819 is a wasteful number, since it uses less digits than its factorization.

20644819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1588076.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 20644819 is about 4543.6570073015. The cubic root of 20644819 is about 274.3281406165.

The spelling of 20644819 in words is "twenty million, six hundred forty-four thousand, eight hundred nineteen".