21620784 has 80 divisors (see below), whose sum is σ = 59559680. Its totient is φ = 6739200.

The previous prime is 21620749. The next prime is 21620789. The reversal of 21620784 is 48702612.

It is not an unprimeable number, because it can be changed into a prime (21620789) 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, 137634 + ... + 137790.

It is an arithmetic number, because the mean of its divisors is an integer number (744496).

Almost surely, 2^21620784 is an apocalyptic number.

21620784 is a gapful number since it is divisible by the number (24) 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 21620784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29779840).

21620784 is an abundant number, since it is smaller than the sum of its proper divisors (37938896).

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

21620784 is a wasteful number, since it uses less digits than its factorization.

21620784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21620784 is about 4649.8154802099. The cubic root of 21620784 is about 278.5846261804.

The spelling of 21620784 in words is "twenty-one million, six hundred twenty thousand, seven hundred eighty-four".