20506640 has 80 divisors (see below), whose sum is σ = 59460480. Its totient is φ = 6389760.

The previous prime is 20506637. The next prime is 20506669. The reversal of 20506640 is 4660502.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4496 + ... + 7824.

It is an arithmetic number, because the mean of its divisors is an integer number (743256).

Almost surely, 2^20506640 is an apocalyptic number.

20506640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20506640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29730240).

20506640 is an abundant number, since it is smaller than the sum of its proper divisors (38953840).

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

20506640 is a wasteful number, since it uses less digits than its factorization.

20506640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3360 (or 3354 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 20506640 is about 4528.4257750349. The cubic root of 20506640 is about 273.7147296497.

The spelling of 20506640 in words is "twenty million, five hundred six thousand, six hundred forty".