21780576 has 72 divisors (see below), whose sum is σ = 64255464. Its totient is φ = 7257600.

The previous prime is 21780571. The next prime is 21780613. The reversal of 21780576 is 67508712.

21780576 is a `hidden beast` number, since 2 + 1 + 7 + 80 + 576 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21780576.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21780571) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6376 + ... + 9176.

It is an arithmetic number, because the mean of its divisors is an integer number (892437).

Almost surely, 2^21780576 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21780576, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32127732).

21780576 is an abundant number, since it is smaller than the sum of its proper divisors (42474888).

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

21780576 is an equidigital number, since it uses as much as digits as its factorization.

21780576 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2826 (or 2806 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 21780576 is about 4666.9664665605. The cubic root of 21780576 is about 279.2692509999.

The spelling of 21780576 in words is "twenty-one million, seven hundred eighty thousand, five hundred seventy-six".