18515961 has 12 divisors (see below), whose sum is σ = 26942292. Its totient is φ = 12253056.

The previous prime is 18515957. The next prime is 18515971. The reversal of 18515961 is 16951581.

18515961 is a `hidden beast` number, since 18 + 51 + 596 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 8555625 + 9960336 = 2925^2 + 3156^2 .

It is not a de Polignac number, because 18515961 - 2² = 18515957 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18515951) 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, 6276 + ... + 8741.

It is an arithmetic number, because the mean of its divisors is an integer number (2245191).

Almost surely, 2^18515961 is an apocalyptic number.

It is an amenable number.

18515961 is a deficient number, since it is larger than the sum of its proper divisors (8426331).

18515961 is a wasteful number, since it uses less digits than its factorization.

18515961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15160 (or 15157 counting only the distinct ones).

The product of its digits is 10800, while the sum is 36.

The square root of 18515961 is about 4303.0176620600. The cubic root of 18515961 is about 264.5546620112.

The spelling of 18515961 in words is "eighteen million, five hundred fifteen thousand, nine hundred sixty-one".