215478851921 has 2 divisors, whose sum is σ = 215478851922. Its totient is φ = 215478851920.

The previous prime is 215478851831. The next prime is 215478851941. The reversal of 215478851921 is 129158874512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 150842908225 + 64635943696 = 388385^2 + 254236^2 .

It is a cyclic number.

It is not a de Polignac number, because 215478851921 - 2³⁰ = 214405110097 is a prime.

It is a super-2 number, since 2×215478851921² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (215478851941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107739425960 + 107739425961.

It is an arithmetic number, because the mean of its divisors is an integer number (107739425961).

Almost surely, 2^215478851921 is an apocalyptic number.

It is an amenable number.

215478851921 is a deficient number, since it is larger than the sum of its proper divisors (1).

215478851921 is an equidigital number, since it uses as much as digits as its factorization.

215478851921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1612800, while the sum is 53.

The spelling of 215478851921 in words is "two hundred fifteen billion, four hundred seventy-eight million, eight hundred fifty-one thousand, nine hundred twenty-one".