16663581 has 24 divisors (see below), whose sum is σ = 26395200. Its totient is φ = 10046400.

The previous prime is 16663541. The next prime is 16663583. The reversal of 16663581 is 18536661.

It is a happy number.

It is not a de Polignac number, because 16663581 - 2⁷ = 16663453 is a prime.

It is a super-2 number, since 2×16663581² = 555349863487122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16663583) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27520 + ... + 28118.

It is an arithmetic number, because the mean of its divisors is an integer number (1099800).

Almost surely, 2^16663581 is an apocalyptic number.

16663581 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16663581 is a deficient number, since it is larger than the sum of its proper divisors (9731619).

16663581 is a wasteful number, since it uses less digits than its factorization.

16663581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 897 (or 894 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 16663581 is about 4082.1049717027. The cubic root of 16663581 is about 255.4207126551.

Subtracting 16663581 from its reverse (18536661), we obtain a triangular number (1873080 = T₁₉₃₅).

The spelling of 16663581 in words is "sixteen million, six hundred sixty-three thousand, five hundred eighty-one".