21061280 has 48 divisors (see below), whose sum is σ = 50168160. Its totient is φ = 8355072.

The previous prime is 21061259. The next prime is 21061309. The reversal of 21061280 is 8216012.

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

It is a congruent number.

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, 21767 + ... + 22713.

It is an arithmetic number, because the mean of its divisors is an integer number (1045170).

Almost surely, 2^21061280 is an apocalyptic number.

21061280 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 21061280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25084080).

21061280 is an abundant number, since it is smaller than the sum of its proper divisors (29106880).

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

21061280 is a wasteful number, since it uses less digits than its factorization.

21061280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1101 (or 1093 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21061280 is about 4589.2570204773. The cubic root of 21061280 is about 276.1605171437.

Adding to 21061280 its reverse (8216012), we get a palindrome (29277292).

The spelling of 21061280 in words is "twenty-one million, sixty-one thousand, two hundred eighty".