19818981 has 36 divisors (see below), whose sum is σ = 35873292. Its totient is φ = 10450944.

The previous prime is 19818973. The next prime is 19818983. The reversal of 19818981 is 18981891.

It can be written as a sum of positive squares in 2 ways, for example, as 1285956 + 18533025 = 1134^2 + 4305^2 .

It is not a de Polignac number, because 19818981 - 2³ = 19818973 is a prime.

It is a super-2 number, since 2×19818981² = 785584015756722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19818983) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 4005 + ... + 7461.

Almost surely, 2^19818981 is an apocalyptic number.

It is an amenable number.

19818981 is a deficient number, since it is larger than the sum of its proper divisors (16054311).

19818981 is a wasteful number, since it uses less digits than its factorization.

19818981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3490 (or 3480 counting only the distinct ones).

The product of its digits is 41472, while the sum is 45.

The square root of 19818981 is about 4451.8514126148. The cubic root of 19818981 is about 270.6203431756.

The spelling of 19818981 in words is "nineteen million, eight hundred eighteen thousand, nine hundred eighty-one".