21318890 has 16 divisors (see below), whose sum is σ = 39004200. Its totient is φ = 8387520.

The previous prime is 21318889. The next prime is 21318911. The reversal of 21318890 is 9881312.

It can be written as a sum of positive squares in 4 ways, for example, as 5166529 + 16152361 = 2273^2 + 4019^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16865 + ... + 18084.

Almost surely, 2^21318890 is an apocalyptic number.

21318890 is a deficient number, since it is larger than the sum of its proper divisors (17685310).

21318890 is a wasteful number, since it uses less digits than its factorization.

21318890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35017.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 21318890 is about 4617.2383520888. The cubic root of 21318890 is about 277.2819053097.

The spelling of 21318890 in words is "twenty-one million, three hundred eighteen thousand, eight hundred ninety".