20809720 has 32 divisors (see below), whose sum is σ = 47822400. Its totient is φ = 8146048.

The previous prime is 20809709. The next prime is 20809729. The reversal of 20809720 is 2790802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3655 + ... + 7414.

It is an arithmetic number, because the mean of its divisors is an integer number (1494450).

Almost surely, 2^20809720 is an apocalyptic number.

20809720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20809720 is an abundant number, since it is smaller than the sum of its proper divisors (27012680).

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

20809720 is a wasteful number, since it uses less digits than its factorization.

20809720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11127 (or 11123 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 20809720 is about 4561.7672014253. The cubic root of 20809720 is about 275.0566054275.

The spelling of 20809720 in words is "twenty million, eight hundred nine thousand, seven hundred twenty".