21317288 has 8 divisors (see below), whose sum is σ = 39969930. Its totient is φ = 10658640.

The previous prime is 21317267. The next prime is 21317327. The reversal of 21317288 is 88271312.

It can be written as a sum of positive squares in only one way, i.e., 17623204 + 3694084 = 4198^2 + 1922^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1332323 + ... + 1332338.

Almost surely, 2^21317288 is an apocalyptic number.

It is an amenable number.

21317288 is a deficient number, since it is larger than the sum of its proper divisors (18652642).

21317288 is a wasteful number, since it uses less digits than its factorization.

21317288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2664667 (or 2664663 counting only the distinct ones).

The product of its digits is 5376, while the sum is 32.

The square root of 21317288 is about 4617.0648685068. The cubic root of 21317288 is about 277.2749597208.

The spelling of 21317288 in words is "twenty-one million, three hundred seventeen thousand, two hundred eighty-eight".