821225891 has 2 divisors, whose sum is σ = 821225892. Its totient is φ = 821225890.

The previous prime is 821225807. The next prime is 821225903. The reversal of 821225891 is 198522128.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-821225891 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (821225191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410612945 + 410612946.

It is an arithmetic number, because the mean of its divisors is an integer number (410612946).

Almost surely, 2^821225891 is an apocalyptic number.

821225891 is a deficient number, since it is larger than the sum of its proper divisors (1).

821225891 is an equidigital number, since it uses as much as digits as its factorization.

821225891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23040, while the sum is 38.

The square root of 821225891 is about 28657.0391178154. The cubic root of 821225891 is about 936.4563617434.

The spelling of 821225891 in words is "eight hundred twenty-one million, two hundred twenty-five thousand, eight hundred ninety-one".