998686921 has 2 divisors, whose sum is σ = 998686922. Its totient is φ = 998686920.

The previous prime is 998686861. The next prime is 998686951. The reversal of 998686921 is 129686899.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 521482896 + 477204025 = 22836^2 + 21845^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-998686921 is a prime.

It is not a weakly prime, because it can be changed into another prime (998686951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499343460 + 499343461.

It is an arithmetic number, because the mean of its divisors is an integer number (499343461).

Almost surely, 2^998686921 is an apocalyptic number.

It is an amenable number.

998686921 is a deficient number, since it is larger than the sum of its proper divisors (1).

998686921 is an equidigital number, since it uses as much as digits as its factorization.

998686921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3359232, while the sum is 58.

The square root of 998686921 is about 31602.0081798610. The cubic root of 998686921 is about 999.5621152850.

The spelling of 998686921 in words is "nine hundred ninety-eight million, six hundred eighty-six thousand, nine hundred twenty-one".