18135981 has 40 divisors (see below), whose sum is σ = 28621824. Its totient is φ = 11430720.

The previous prime is 18135979. The next prime is 18136003. The reversal of 18135981 is 18953181.

It is not a de Polignac number, because 18135981 - 2¹ = 18135979 is a prime.

It is a super-2 number, since 2×18135981² = 657827613664722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18135941) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 142740 + ... + 142866.

Almost surely, 2^18135981 is an apocalyptic number.

It is an amenable number.

18135981 is a deficient number, since it is larger than the sum of its proper divisors (10485843).

18135981 is a wasteful number, since it uses less digits than its factorization.

18135981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223 (or 214 counting only the distinct ones).

The product of its digits is 8640, while the sum is 36.

The square root of 18135981 is about 4258.6360492533. The cubic root of 18135981 is about 262.7324308678.

The spelling of 18135981 in words is "eighteen million, one hundred thirty-five thousand, nine hundred eighty-one".