20021840 has 40 divisors (see below), whose sum is σ = 47005920. Its totient is φ = 7930496.

The previous prime is 20021831. The next prime is 20021843. The reversal of 20021840 is 4812002.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20021843) 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, 7391 + ... + 9729.

It is an arithmetic number, because the mean of its divisors is an integer number (1175148).

Almost surely, 2^20021840 is an apocalyptic number.

20021840 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 20021840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23502960).

20021840 is an abundant number, since it is smaller than the sum of its proper divisors (26984080).

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

20021840 is a wasteful number, since it uses less digits than its factorization.

20021840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2459 (or 2453 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 20021840 is about 4474.5770749871. The cubic root of 20021840 is about 271.5405305176.

Adding to 20021840 its reverse (4812002), we get a palindrome (24833842).

The spelling of 20021840 in words is "twenty million, twenty-one thousand, eight hundred forty".