21317031 has 24 divisors (see below), whose sum is σ = 34323120. Its totient is φ = 12669696.

The previous prime is 21317029. The next prime is 21317033. The reversal of 21317031 is 13071312.

It is an interprime number because it is at equal distance from previous prime (21317029) and next prime (21317033).

It is not a de Polignac number, because 21317031 - 2¹ = 21317029 is a prime.

It is a super-2 number, since 2×21317031² = 908831621309922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21316995 and 21317013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21317033) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 760 + ... + 6573.

It is an arithmetic number, because the mean of its divisors is an integer number (1430130).

Almost surely, 2^21317031 is an apocalyptic number.

21317031 is a deficient number, since it is larger than the sum of its proper divisors (13006089).

21317031 is a wasteful number, since it uses less digits than its factorization.

21317031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7375 (or 7372 counting only the distinct ones).

The product of its (nonzero) digits is 126, while the sum is 18.

The square root of 21317031 is about 4617.0370368885. The cubic root of 21317031 is about 277.2738454460.

Adding to 21317031 its reverse (13071312), we get a palindrome (34388343).

The spelling of 21317031 in words is "twenty-one million, three hundred seventeen thousand, thirty-one".