21317137 has 4 divisors (see below), whose sum is σ = 21356656. Its totient is φ = 21277620.

The previous prime is 21317129. The next prime is 21317141. The reversal of 21317137 is 73171312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21317137 - 2³ = 21317129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21317147) 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, 18939 + ... + 20032.

It is an arithmetic number, because the mean of its divisors is an integer number (5339164).

Almost surely, 2^21317137 is an apocalyptic number.

It is an amenable number.

21317137 is a deficient number, since it is larger than the sum of its proper divisors (39519).

21317137 is an equidigital number, since it uses as much as digits as its factorization.

21317137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39518.

The product of its digits is 882, while the sum is 25.

The square root of 21317137 is about 4617.0485160977. The cubic root of 21317137 is about 277.2743050312.

Adding to 21317137 its reverse (73171312), we get a palindrome (94488449).

The spelling of 21317137 in words is "twenty-one million, three hundred seventeen thousand, one hundred thirty-seven".