20821380 has 96 divisors (see below), whose sum is σ = 61133184. Its totient is φ = 5289984.

The previous prime is 20821373. The next prime is 20821387. The reversal of 20821380 is 8312802.

It is an interprime number because it is at equal distance from previous prime (20821373) and next prime (20821387).

It is a self number, because there is not a number n which added to its sum of digits gives 20821380.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 184204 + ... + 184316.

It is an arithmetic number, because the mean of its divisors is an integer number (636804).

Almost surely, 2^20821380 is an apocalyptic number.

20821380 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 20821380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30566592).

20821380 is an abundant number, since it is smaller than the sum of its proper divisors (40311804).

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

20821380 is a wasteful number, since it uses less digits than its factorization.

20821380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245 (or 243 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 20821380 is about 4563.0450359382. The cubic root of 20821380 is about 275.1079686238.

The spelling of 20821380 in words is "twenty million, eight hundred twenty-one thousand, three hundred eighty".