20206640 has 20 divisors (see below), whose sum is σ = 46980624. Its totient is φ = 8082624.

The previous prime is 20206639. The next prime is 20206651. The reversal of 20206640 is 4660202.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 126212 + ... + 126371.

Almost surely, 2^20206640 is an apocalyptic number.

20206640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20206640 is an abundant number, since it is smaller than the sum of its proper divisors (26773984).

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

20206640 is a wasteful number, since it uses less digits than its factorization.

20206640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252596 (or 252590 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 20206640 is about 4495.1796404593. The cubic root of 20206640 is about 272.3734058332.

Adding to 20206640 its reverse (4660202), we get a palindrome (24866842).

The spelling of 20206640 in words is "twenty million, two hundred six thousand, six hundred forty".