20821340 has 48 divisors (see below), whose sum is σ = 46452000. Its totient is φ = 7817472.

The previous prime is 20821327. The next prime is 20821349. The reversal of 20821340 is 4312802.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821349) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 59486 + ... + 59834.

It is an arithmetic number, because the mean of its divisors is an integer number (967750).

Almost surely, 2^20821340 is an apocalyptic number.

20821340 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 20821340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23226000).

20821340 is an abundant number, since it is smaller than the sum of its proper divisors (25630660).

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

20821340 is a wasteful number, since it uses less digits than its factorization.

20821340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534 (or 532 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 20821340 is about 4563.0406528980. The cubic root of 20821340 is about 275.1077924535.

The spelling of 20821340 in words is "twenty million, eight hundred twenty-one thousand, three hundred forty".