1998657 has 6 divisors (see below), whose sum is σ = 2886962. Its totient is φ = 1332432.

The previous prime is 1998643. The next prime is 1998679. The reversal of 1998657 is 7568991.

It can be written as a sum of positive squares in only one way, i.e., 1252161 + 746496 = 1119^2 + 864^2 .

It is not a de Polignac number, because 1998657 - 2⁴ = 1998641 is a prime.

It is a Duffinian number.

1998657 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1998617) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 111028 + ... + 111045.

2^1998657 is an apocalyptic number.

It is an amenable number.

1998657 is a deficient number, since it is larger than the sum of its proper divisors (888305).

1998657 is a wasteful number, since it uses less digits than its factorization.

1998657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222079 (or 222076 counting only the distinct ones).

The product of its digits is 136080, while the sum is 45.

The square root of 1998657 is about 1413.7386604320. The cubic root of 1998657 is about 125.9638974419.

The spelling of 1998657 in words is "one million, nine hundred ninety-eight thousand, six hundred fifty-seven".