21317263 has 4 divisors (see below), whose sum is σ = 23255208. Its totient is φ = 19379320.

The previous prime is 21317249. The next prime is 21317267. The reversal of 21317263 is 36271312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21317263 - 2⁹ = 21316751 is a prime.

It is a super-2 number, since 2×21317263² = 908851403622338, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21317267) 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, 968956 + ... + 968977.

It is an arithmetic number, because the mean of its divisors is an integer number (5813802).

Almost surely, 2^21317263 is an apocalyptic number.

21317263 is a deficient number, since it is larger than the sum of its proper divisors (1937945).

21317263 is a wasteful number, since it uses less digits than its factorization.

21317263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1937944.

The product of its digits is 1512, while the sum is 25.

The square root of 21317263 is about 4617.0621611583. The cubic root of 21317263 is about 277.2748513287.

Adding to 21317263 its reverse (36271312), we get a palindrome (57588575).

The spelling of 21317263 in words is "twenty-one million, three hundred seventeen thousand, two hundred sixty-three".