521821728 has 72 divisors (see below), whose sum is σ = 1506134448. Its totient is φ = 171338112.

The previous prime is 521821709. The next prime is 521821753. The reversal of 521821728 is 827128125.

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

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

It is a junction number, because it is equal to n+sod(n) for n = 521821692 and 521821701.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5775 + ... + 32817.

It is an arithmetic number, because the mean of its divisors is an integer number (20918534).

Almost surely, 2^521821728 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 521821728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (753067224).

521821728 is an abundant number, since it is smaller than the sum of its proper divisors (984312720).

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

521821728 is a wasteful number, since it uses less digits than its factorization.

521821728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27126 (or 27115 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 521821728 is about 22843.4176077049. The cubic root of 521821728 is about 805.0831173259.

The spelling of 521821728 in words is "five hundred twenty-one million, eight hundred twenty-one thousand, seven hundred twenty-eight".