18819981 has 12 divisors (see below), whose sum is σ = 27237600. Its totient is φ = 12522120.

The previous prime is 18819979. The next prime is 18819989. The reversal of 18819981 is 18991881.

It is not a de Polignac number, because 18819981 - 2¹ = 18819979 is a prime.

It is a super-2 number, since 2×18819981² = 708383369680722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18819989) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3646 + ... + 7136.

It is an arithmetic number, because the mean of its divisors is an integer number (2269800).

Almost surely, 2^18819981 is an apocalyptic number.

It is an amenable number.

18819981 is a deficient number, since it is larger than the sum of its proper divisors (8417619).

18819981 is a wasteful number, since it uses less digits than its factorization.

18819981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4096 (or 4093 counting only the distinct ones).

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

The square root of 18819981 is about 4338.2002028491. The cubic root of 18819981 is about 265.9947471026.

The spelling of 18819981 in words is "eighteen million, eight hundred nineteen thousand, nine hundred eighty-one".