20709840 has 40 divisors (see below), whose sum is σ = 64201248. Its totient is φ = 5522560.

The previous prime is 20709833. The next prime is 20709841. The reversal of 20709840 is 4890702.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 20709798 and 20709807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20709841) 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, 42906 + ... + 43385.

Almost surely, 2^20709840 is an apocalyptic number.

20709840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20709840 is an abundant number, since it is smaller than the sum of its proper divisors (43491408).

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

20709840 is a wasteful number, since it uses less digits than its factorization.

20709840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86307 (or 86301 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 20709840 is about 4550.8065219255. The cubic root of 20709840 is about 274.6158382501.

The spelling of 20709840 in words is "twenty million, seven hundred nine thousand, eight hundred forty".