20640566 has 4 divisors (see below), whose sum is σ = 30960852. Its totient is φ = 10320282.

The previous prime is 20640563. The next prime is 20640577. The reversal of 20640566 is 66504602.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5160140 + ... + 5160143.

It is an arithmetic number, because the mean of its divisors is an integer number (7740213).

Almost surely, 2^20640566 is an apocalyptic number.

20640566 is a deficient number, since it is larger than the sum of its proper divisors (10320286).

20640566 is a wasteful number, since it uses less digits than its factorization.

20640566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10320285.

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 20640566 is about 4543.1889681148. The cubic root of 20640566 is about 274.3093013828.

The spelling of 20640566 in words is "twenty million, six hundred forty thousand, five hundred sixty-six".