20821280 has 48 divisors (see below), whose sum is σ = 49533120. Its totient is φ = 8270592.

The previous prime is 20821261. The next prime is 20821291. The reversal of 20821280 is 8212802.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28277 + ... + 29003.

It is an arithmetic number, because the mean of its divisors is an integer number (1031940).

Almost surely, 2^20821280 is an apocalyptic number.

20821280 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 20821280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24766560).

20821280 is an abundant number, since it is smaller than the sum of its proper divisors (28711840).

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

20821280 is a wasteful number, since it uses less digits than its factorization.

20821280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 921 (or 913 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 23.

The square root of 20821280 is about 4563.0340783299. The cubic root of 20821280 is about 275.1075281977.

The spelling of 20821280 in words is "twenty million, eight hundred twenty-one thousand, two hundred eighty".