20640819 has 4 divisors (see below), whose sum is σ = 27521096. Its totient is φ = 13760544.

The previous prime is 20640793. The next prime is 20640827. The reversal of 20640819 is 91804602.

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

It is not a de Polignac number, because 20640819 - 2⁵ = 20640787 is a prime.

It is a super-2 number, since 2×20640819² = 852086817981522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20640869) 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, 3440134 + ... + 3440139.

It is an arithmetic number, because the mean of its divisors is an integer number (6880274).

Almost surely, 2^20640819 is an apocalyptic number.

20640819 is a deficient number, since it is larger than the sum of its proper divisors (6880277).

20640819 is an equidigital number, since it uses as much as digits as its factorization.

20640819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6880276.

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 20640819 is about 4543.2168119076. The cubic root of 20640819 is about 274.3104221526.

The spelling of 20640819 in words is "twenty million, six hundred forty thousand, eight hundred nineteen".