821587961 has 2 divisors, whose sum is σ = 821587962. Its totient is φ = 821587960.

The previous prime is 821587957. The next prime is 821587979. The reversal of 821587961 is 169785128.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 426174736 + 395413225 = 20644^2 + 19885^2 .

It is a cyclic number.

It is not a de Polignac number, because 821587961 - 2² = 821587957 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (821587901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410793980 + 410793981.

It is an arithmetic number, because the mean of its divisors is an integer number (410793981).

Almost surely, 2^821587961 is an apocalyptic number.

It is an amenable number.

821587961 is a deficient number, since it is larger than the sum of its proper divisors (1).

821587961 is an equidigital number, since it uses as much as digits as its factorization.

821587961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 241920, while the sum is 47.

The square root of 821587961 is about 28663.3557177104. The cubic root of 821587961 is about 936.5939661635.

The spelling of 821587961 in words is "eight hundred twenty-one million, five hundred eighty-seven thousand, nine hundred sixty-one".