19998657 has 28 divisors (see below), whose sum is σ = 34276480. Its totient is φ = 11424888.

The previous prime is 19998653. The next prime is 19998677. The reversal of 19998657 is 75689991.

It is not a de Polignac number, because 19998657 - 2² = 19998653 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19998653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 3144 + ... + 7062.

It is an arithmetic number, because the mean of its divisors is an integer number (1224160).

Almost surely, 2^19998657 is an apocalyptic number.

It is an amenable number.

19998657 is a deficient number, since it is larger than the sum of its proper divisors (14277823).

19998657 is an frugal number, since it uses more digits than its factorization.

19998657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3944 (or 3929 counting only the distinct ones).

The product of its digits is 1224720, while the sum is 54.

The square root of 19998657 is about 4471.9858005141. The cubic root of 19998657 is about 271.4356857521.

The spelling of 19998657 in words is "nineteen million, nine hundred ninety-eight thousand, six hundred fifty-seven".