19981663 has 4 divisors (see below), whose sum is σ = 21518728. Its totient is φ = 18444600.

The previous prime is 19981649. The next prime is 19981693. The reversal of 19981663 is 36618991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 36618991 = 487 ⋅75193.

It is a cyclic number.

It is not a de Polignac number, because 19981663 - 2⁹ = 19981151 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19981693) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 768513 + ... + 768538.

It is an arithmetic number, because the mean of its divisors is an integer number (5379682).

Almost surely, 2^19981663 is an apocalyptic number.

19981663 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

19981663 is a deficient number, since it is larger than the sum of its proper divisors (1537065).

19981663 is a wasteful number, since it uses less digits than its factorization.

19981663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1537064.

The product of its digits is 69984, while the sum is 43.

The square root of 19981663 is about 4470.0853459414. The cubic root of 19981663 is about 271.3587791671.

The spelling of 19981663 in words is "nineteen million, nine hundred eighty-one thousand, six hundred sixty-three".