19813981 has 16 divisors (see below), whose sum is σ = 22489920. Its totient is φ = 17297280.

The previous prime is 19813967. The next prime is 19813987. The reversal of 19813981 is 18931891.

It is a happy number.

It is not a de Polignac number, because 19813981 - 2⁵ = 19813949 is a prime.

It is a super-3 number, since 3×19813981³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19813987) 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, 35950 + ... + 36496.

It is an arithmetic number, because the mean of its divisors is an integer number (1405620).

Almost surely, 2^19813981 is an apocalyptic number.

19813981 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19813981 is a deficient number, since it is larger than the sum of its proper divisors (2675939).

19813981 is a wasteful number, since it uses less digits than its factorization.

19813981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 684.

The product of its digits is 15552, while the sum is 40.

The square root of 19813981 is about 4451.2898130767. The cubic root of 19813981 is about 270.5975835877.

The spelling of 19813981 in words is "nineteen million, eight hundred thirteen thousand, nine hundred eighty-one".