21780528 has 160 divisors (see below), whose sum is σ = 71995392. Its totient is φ = 5510400.

The previous prime is 21780523. The next prime is 21780533. The reversal of 21780528 is 82508712.

It is an interprime number because it is at equal distance from previous prime (21780523) and next prime (21780533).

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21780523) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 262375 + ... + 262457.

Almost surely, 2^21780528 is an apocalyptic number.

21780528 is a gapful number since it is divisible by the number (28) 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 21780528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35997696).

21780528 is an abundant number, since it is smaller than the sum of its proper divisors (50214864).

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

21780528 is a wasteful number, since it uses less digits than its factorization.

21780528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 183 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 21780528 is about 4666.9613240309. The cubic root of 21780528 is about 279.2690458487.

The spelling of 21780528 in words is "twenty-one million, seven hundred eighty thousand, five hundred twenty-eight".