20640555 has 64 divisors (see below), whose sum is σ = 41664000. Its totient is φ = 9611136.

The previous prime is 20640553. The next prime is 20640563. The reversal of 20640555 is 55504602.

20640555 is a `hidden beast` number, since 206 + 405 + 55 = 666.

It is not a de Polignac number, because 20640555 - 2¹ = 20640553 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (20640553) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 33036 + ... + 33654.

It is an arithmetic number, because the mean of its divisors is an integer number (651000).

Almost surely, 2^20640555 is an apocalyptic number.

20640555 is an abundant number, since it is smaller than the sum of its proper divisors (21023445).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20640555 is a wasteful number, since it uses less digits than its factorization.

20640555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 665 (or 659 counting only the distinct ones).

The product of its (nonzero) digits is 6000, while the sum is 27.

The square root of 20640555 is about 4543.1877575112. The cubic root of 20640555 is about 274.3092526535.

The spelling of 20640555 in words is "twenty million, six hundred forty thousand, five hundred fifty-five".