20640340 has 48 divisors (see below), whose sum is σ = 49795200. Its totient is φ = 7039872.

The previous prime is 20640331. The next prime is 20640391. The reversal of 20640340 is 4304602.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 52866 + ... + 53254.

It is an arithmetic number, because the mean of its divisors is an integer number (1037400).

Almost surely, 2^20640340 is an apocalyptic number.

20640340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20640340 is an abundant number, since it is smaller than the sum of its proper divisors (29154860).

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

20640340 is a wasteful number, since it uses less digits than its factorization.

20640340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 784 (or 782 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 19.

The square root of 20640340 is about 4543.1640956496. The cubic root of 20640340 is about 274.3083002131.

Adding to 20640340 its reverse (4304602), we get a palindrome (24944942).

The spelling of 20640340 in words is "twenty million, six hundred forty thousand, three hundred forty".