20861440 has 80 divisors (see below), whose sum is σ = 51927480. Its totient is φ = 8028160.

The previous prime is 20861417. The next prime is 20861441. The reversal of 20861440 is 4416802.

It can be written as a sum of positive squares in 4 ways, for example, as 18249984 + 2611456 = 4272^2 + 1616^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20861441) 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, 74100 + ... + 74380.

Almost surely, 2^20861440 is an apocalyptic number.

20861440 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 20861440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25963740).

20861440 is an abundant number, since it is smaller than the sum of its proper divisors (31066040).

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

20861440 is an equidigital number, since it uses as much as digits as its factorization.

20861440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333 (or 317 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 20861440 is about 4567.4325391844. The cubic root of 20861440 is about 275.2842900269.

The spelling of 20861440 in words is "twenty million, eight hundred sixty-one thousand, four hundred forty".