820917121 has 2 divisors, whose sum is σ = 820917122. Its totient is φ = 820917120.

The previous prime is 820917037. The next prime is 820917137. The reversal of 820917121 is 121719028.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 574081600 + 246835521 = 23960^2 + 15711^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-820917121 is a prime.

It is not a weakly prime, because it can be changed into another prime (820917151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410458560 + 410458561.

It is an arithmetic number, because the mean of its divisors is an integer number (410458561).

Almost surely, 2^820917121 is an apocalyptic number.

It is an amenable number.

820917121 is a deficient number, since it is larger than the sum of its proper divisors (1).

820917121 is an equidigital number, since it uses as much as digits as its factorization.

820917121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 31.

The square root of 820917121 is about 28651.6512787658. The cubic root of 820917121 is about 936.3389819902.

The spelling of 820917121 in words is "eight hundred twenty million, nine hundred seventeen thousand, one hundred twenty-one".