18981566 has 8 divisors (see below), whose sum is σ = 28873584. Its totient is φ = 9357040.

The previous prime is 18981563. The next prime is 18981577. The reversal of 18981566 is 66518981.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18981563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66695 + ... + 66978.

It is an arithmetic number, because the mean of its divisors is an integer number (3609198).

Almost surely, 2^18981566 is an apocalyptic number.

18981566 is a deficient number, since it is larger than the sum of its proper divisors (9892018).

18981566 is a wasteful number, since it uses less digits than its factorization.

18981566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133746.

The product of its digits is 103680, while the sum is 44.

The square root of 18981566 is about 4356.7839055891. The cubic root of 18981566 is about 266.7538399028.

The spelling of 18981566 in words is "eighteen million, nine hundred eighty-one thousand, five hundred sixty-six".