998555581 has 2 divisors, whose sum is σ = 998555582. Its totient is φ = 998555580.

The previous prime is 998555549. The next prime is 998555587. The reversal of 998555581 is 185555899.

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., 883872900 + 114682681 = 29730^2 + 10709^2 .

It is a cyclic number.

It is not a de Polignac number, because 998555581 - 2⁵ = 998555549 is a prime.

It is a super-2 number, since 2×998555581² = 1994226496692495122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (998555587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499277790 + 499277791.

It is an arithmetic number, because the mean of its divisors is an integer number (499277791).

Almost surely, 2^998555581 is an apocalyptic number.

It is an amenable number.

998555581 is a deficient number, since it is larger than the sum of its proper divisors (1).

998555581 is an equidigital number, since it uses as much as digits as its factorization.

998555581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3240000, while the sum is 55.

The square root of 998555581 is about 31599.9300790366. The cubic root of 998555581 is about 999.5182949975.

The spelling of 998555581 in words is "nine hundred ninety-eight million, five hundred fifty-five thousand, five hundred eighty-one".