19981723 has 2 divisors, whose sum is σ = 19981724. Its totient is φ = 19981722.

The previous prime is 19981697. The next prime is 19981727. The reversal of 19981723 is 32718991.

It is a strong prime.

It is an emirp because it is prime and its reverse (32718991) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19981723 is a prime.

It is not a weakly prime, because it can be changed into another prime (19981727) 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 as a sum of consecutive naturals, namely, 9990861 + 9990862.

It is an arithmetic number, because the mean of its divisors is an integer number (9990862).

Almost surely, 2^19981723 is an apocalyptic number.

19981723 is a deficient number, since it is larger than the sum of its proper divisors (1).

19981723 is an equidigital number, since it uses as much as digits as its factorization.

19981723 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 40.

The square root of 19981723 is about 4470.0920572176. The cubic root of 19981723 is about 271.3590507746.

It can be divided in two parts, 1998 and 1723, that added together give a square (3721 = 61²).

The spelling of 19981723 in words is "nineteen million, nine hundred eighty-one thousand, seven hundred twenty-three".