821661225 has 96 divisors (see below), whose sum is σ = 1716080640. Its totient is φ = 336960000.

The previous prime is 821661163. The next prime is 821661229. The reversal of 821661225 is 522166128.

821661225 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 821661225 - 2⁸ = 821660969 is a prime.

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (821661229) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 455325 + ... + 457125.

It is an arithmetic number, because the mean of its divisors is an integer number (17875840).

Almost surely, 2^821661225 is an apocalyptic number.

It is an amenable number.

821661225 is an abundant number, since it is smaller than the sum of its proper divisors (894419415).

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

821661225 is a wasteful number, since it uses less digits than its factorization.

821661225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1911 (or 1906 counting only the distinct ones).

The product of its digits is 11520, while the sum is 33.

The square root of 821661225 is about 28664.6336972933. The cubic root of 821661225 is about 936.6218051712.

The spelling of 821661225 in words is "eight hundred twenty-one million, six hundred sixty-one thousand, two hundred twenty-five".