998891581 has 2 divisors, whose sum is σ = 998891582. Its totient is φ = 998891580.

The previous prime is 998891557. The next prime is 998891603. The reversal of 998891581 is 185198899.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 856089081 + 142802500 = 29259^2 + 11950^2 .

It is a cyclic number.

It is not a de Polignac number, because 998891581 - 2¹⁵ = 998858813 is a prime.

It is a super-2 number, since 2×998891581² = 1995568781185359122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (998891521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499445790 + 499445791.

It is an arithmetic number, because the mean of its divisors is an integer number (499445791).

Almost surely, 2^998891581 is an apocalyptic number.

It is an amenable number.

998891581 is a deficient number, since it is larger than the sum of its proper divisors (1).

998891581 is an equidigital number, since it uses as much as digits as its factorization.

998891581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1866240, while the sum is 58.

The square root of 998891581 is about 31605.2460993424. The cubic root of 998891581 is about 999.6303904056.

The spelling of 998891581 in words is "nine hundred ninety-eight million, eight hundred ninety-one thousand, five hundred eighty-one".