978557303755921 has 2 divisors, whose sum is σ = 978557303755922. Its totient is φ = 978557303755920.

The previous prime is 978557303755873. The next prime is 978557303755949. The reversal of 978557303755921 is 129557303755879.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 625640163840000 + 352917139915921 = 25012800^2 + 18786089^2 .

It is an emirp because it is prime and its reverse (129557303755879) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 978557303755921 - 2¹¹ = 978557303753873 is a prime.

It is not a weakly prime, because it can be changed into another prime (978557303755321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 489278651877960 + 489278651877961.

It is an arithmetic number, because the mean of its divisors is an integer number (489278651877961).

Almost surely, 2^{978557303755921} is an apocalyptic number.

It is an amenable number.

978557303755921 is a deficient number, since it is larger than the sum of its proper divisors (1).

978557303755921 is an equidigital number, since it uses as much as digits as its factorization.

978557303755921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2500470000, while the sum is 76.

The spelling of 978557303755921 in words is "nine hundred seventy-eight trillion, five hundred fifty-seven billion, three hundred three million, seven hundred fifty-five thousand, nine hundred twenty-one".