20815819 has 4 divisors (see below), whose sum is σ = 21066696. Its totient is φ = 20564944.

The previous prime is 20815807. The next prime is 20815831. The reversal of 20815819 is 91851802.

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

It is an interprime number because it is at equal distance from previous prime (20815807) and next prime (20815831).

It is a cyclic number.

It is not a de Polignac number, because 20815819 - 2²³ = 12427211 is a prime.

It is a super-2 number, since 2×20815819² = 866596641281522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20815859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 125314 + ... + 125479.

It is an arithmetic number, because the mean of its divisors is an integer number (5266674).

Almost surely, 2^20815819 is an apocalyptic number.

20815819 is a deficient number, since it is larger than the sum of its proper divisors (250877).

20815819 is an equidigital number, since it uses as much as digits as its factorization.

20815819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250876.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 20815819 is about 4562.4356433817. The cubic root of 20815819 is about 275.0834743839.

The spelling of 20815819 in words is "twenty million, eight hundred fifteen thousand, eight hundred nineteen".