998665551 has 16 divisors (see below), whose sum is σ = 1593313120. Its totient is φ = 614563200.

The previous prime is 998665487. The next prime is 998665559. The reversal of 998665551 is 155566899.

998665551 is a `hidden beast` number, since 9 + 9 + 86 + 6 + 5 + 551 = 666.

It is not a de Polignac number, because 998665551 - 2⁶ = 998665487 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (998665559) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1422250 + ... + 1422951.

It is an arithmetic number, because the mean of its divisors is an integer number (99582070).

Almost surely, 2^998665551 is an apocalyptic number.

998665551 is a deficient number, since it is larger than the sum of its proper divisors (594647569).

998665551 is a wasteful number, since it uses less digits than its factorization.

998665551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2845223 (or 2845217 counting only the distinct ones).

The product of its digits is 2916000, while the sum is 54.

The square root of 998665551 is about 31601.6700666278. The cubic root of 998665551 is about 999.5549856583.

The spelling of 998665551 in words is "nine hundred ninety-eight million, six hundred sixty-five thousand, five hundred fifty-one".