978861557 has 2 divisors, whose sum is σ = 978861558. Its totient is φ = 978861556.

The previous prime is 978861539. The next prime is 978861601. The reversal of 978861557 is 755168879.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 796989361 + 181872196 = 28231^2 + 13486^2 .

It is an emirp because it is prime and its reverse (755168879) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 978861557 - 2⁶ = 978861493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (978866557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 489430778 + 489430779.

It is an arithmetic number, because the mean of its divisors is an integer number (489430779).

Almost surely, 2^978861557 is an apocalyptic number.

It is an amenable number.

978861557 is a deficient number, since it is larger than the sum of its proper divisors (1).

978861557 is an equidigital number, since it uses as much as digits as its factorization.

978861557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4233600, while the sum is 56.

The square root of 978861557 is about 31286.7632873712. The cubic root of 978861557 is about 992.9036127429.

The spelling of 978861557 in words is "nine hundred seventy-eight million, eight hundred sixty-one thousand, five hundred fifty-seven".