20921280 has 224 divisors, whose sum is σ = 74127360. Its totient is φ = 4976640.

The previous prime is 20921269. The next prime is 20921309. The reversal of 20921280 is 8212902.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 20921280.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 565422 + ... + 565458.

Almost surely, 2^20921280 is an apocalyptic number.

20921280 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 20921280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37063680).

20921280 is an abundant number, since it is smaller than the sum of its proper divisors (53206080).

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

20921280 is a wasteful number, since it uses less digits than its factorization.

20921280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107 (or 97 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 20921280 is about 4573.9785745016. The cubic root of 20921280 is about 275.5472518406.

The spelling of 20921280 in words is "twenty million, nine hundred twenty-one thousand, two hundred eighty".