1821687961 has 2 divisors, whose sum is σ = 1821687962. Its totient is φ = 1821687960.

The previous prime is 1821687943. The next prime is 1821687997. The reversal of 1821687961 is 1697861281.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1719677961 + 102010000 = 41469^2 + 10100^2 .

It is a cyclic number.

It is not a de Polignac number, because 1821687961 - 2⁹ = 1821687449 is a prime.

It is not a weakly prime, because it can be changed into another prime (1821687941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910843980 + 910843981.

It is an arithmetic number, because the mean of its divisors is an integer number (910843981).

Almost surely, 2^1821687961 is an apocalyptic number.

It is an amenable number.

1821687961 is a deficient number, since it is larger than the sum of its proper divisors (1).

1821687961 is an equidigital number, since it uses as much as digits as its factorization.

1821687961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 290304, while the sum is 49.

The square root of 1821687961 is about 42681.2366385980. The cubic root of 1821687961 is about 1221.3064838117.

The spelling of 1821687961 in words is "one billion, eight hundred twenty-one million, six hundred eighty-seven thousand, nine hundred sixty-one".