18201981 has 36 divisors (see below), whose sum is σ = 29882592. Its totient is φ = 9853704.

The previous prime is 18201979. The next prime is 18202003. The reversal of 18201981 is 18910281.

It is not a de Polignac number, because 18201981 - 2¹ = 18201979 is a prime.

It is a super-2 number, since 2×18201981² = 662624224648722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18201941) 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, 957990 + ... + 958008.

It is an arithmetic number, because the mean of its divisors is an integer number (830072).

Almost surely, 2^18201981 is an apocalyptic number.

It is an amenable number.

18201981 is a deficient number, since it is larger than the sum of its proper divisors (11680611).

18201981 is an frugal number, since it uses more digits than its factorization.

18201981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76 (or 29 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 18201981 is about 4266.3779720039. The cubic root of 18201981 is about 263.0507547570.

The spelling of 18201981 in words is "eighteen million, two hundred one thousand, nine hundred eighty-one".